Keeping things simple

* {
    box-sizing: border-box; /* you absolutely need this - look it up */
}

html body { /* there's no need to say "any body inside of an html"
    /* you can just use 'body' as the selector */
    font-family: Arial, Helvetica, sans-serif;
    width: 100vw; /* it's already 100% width by default */
    height: 100vh; /* should likely be min-height */
    margin: 0px;
    padding: 0px; /* these should likely be taken care of by a css-reset (I use meyer-reset) */
}

.container { /* container is a bad name. everything is a container */
    width: 100%;
    height: 100%; /* these are suspect - why are they needed ? */
    display: flex;
    flex-direction: row;
}

.left-container::-webkit-scrollbar {
    display: none;
}

.left-container { /* left-container is a bad name - what if it's not left at a different break point? also / I don't know what it's for. Is it a 'sidebar' - or what is its actual purpose? name it with that */
    -ms-overflow-style: none;
    scrollbar-width: none;
    background: rgb(34, 193, 195);
    background: linear-gradient(
        0deg,
        rgba(34, 193, 195, 1) 0%,
        rgba(253, 187, 45, 1) 100%
    );
    width: 35%;
    height: 100%; /* likely not needed... based of of a previous decision */
    max-height: fit-content; /* maybe needed */
    overflow-y: scroll;
}

h1 {
    font-size: 2vw; /* probably should use clamp here for min/max */
    color: white; /* should be a custom-property for site-wide colors */
    position: relative;
    top: 40%; /* sounds scary! */
    text-align: center;
}

.memory-container { /* again... "container" doesn't help me know what this is */
    width: 100%; /* aren't all block-level elements width:100% already? */
    max-height: fit-content;
    min-height: 400px;
}

.memory-div::-webkit-scrollbar {
    display: none; /* this sounds like bad news */
}
.memory-div { /* even worse name than container */
    -ms-overflow-style: none;
    scrollbar-width: none;
    width: 90%;
    max-height: 100px;
    min-height: 60px;
    background: rgba(255, 213, 0, 0.08);
    border-radius: 16px;
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(3.6px);
    -webkit-backdrop-filter: blur(3.6px);
    border: 1px solid rgba(255, 213, 0, 0.19);
    margin: 20px;
    word-wrap: break-word;
    overflow: scroll;
    display: flex;
    flex-direction: row;
}

.memory-div:hover {
    background: rgba(152, 128, 6, 0.08);
    border: 2px solid white;
}

.paragraph-left { /* again - keep the visual out of the selector names */
    display: flex;
    width: 72%;
    color: white;
    text-align: center; /* centered paragraphs? */
    font-size: x-large; /* probably don't use these... */
    justify-content: center;
    flex-direction: row;
    margin: 14px;
    word-break: break-word;
}
.fa-sharp { /* I'd suggest SVG sprite over fa as it seems to break a lot */
    display: flex;
    font-size: 40px;
    color: white;
    margin: 10px;
    width: 30px;
    justify-content: center;
    position: sticky;
}

#trash { /* avoid ids in your CSS */
    display: flex;
    margin-top: 15px;
    font-size: x-large;
    color: white;
}
#trash:hover {
    color: rgb(211, 211, 211);
}

.popup {
    width: 79vw; /* this seems very 'magic' and is suspect */
    height: 100vh;
    position: fixed;
    left: 30%;
    background: rgb(2, 233, 237);
    background: linear-gradient(
        0deg,
        rgb(0, 251, 255) 0%,
        rgb(244, 172, 18) 100%
    );
    opacity: 90%;
    z-index: 1;
    display: none;
}

.popup input {
    width: 600px;
    height: 150px;
    border-radius: 10px;
    position: relative;
    left: 240px; /* this positioning seems scary and likey to break */
    top: 280px; /* how about using grid instead */
    border: 2px solid #ffffff; /* border width and color should be custom -properties */
    background-color: #fdbb2d;
    color: white;
}

.popup h1 {
    display: inline-block;
    left: 160px; /* brittle */
    top: 20%;
    font-size: 40px;
    color: white;
    text-align: center;
    font-family: Arial, Helvetica, sans-serif; /* already on the body in your case */
    opacity: 100%; /* why? */
}

.add-memory-button { /* could also be button.add-memory  - but either way - this was a good selector because I knew what it did / but is the "add" really relevant - should there be a global .button type class? */
    width: 220px;
    height: 40px;
    position: absolute; /* there is probably a better way for this */
    bottom: 200px;
    left: 420px;
    background-color: rgba(253, 187, 45, 1);
    border: 1px solid white;
    border-radius: 10px;
    color: white;
    font-size: 20px;
}

.popup button:hover {
    background-color: rgb(247, 168, 0);
    border: 2px solid white;
}
.popup button:active {
    background-color: rgb(194, 132, 0);
    border: 2px solid white;
}

.close-popup { /* these should probably be scoped to the pop-up module or something so that they aren't global */
    color: white;
    font-size: 40px;
    position: relative;
    left: 940px;
    top: 40px;
}
.close-popup:hover {
    color: rgb(210, 210, 210);
    font-size: 40px;
    position: relative;
}
#map {
    width: 80%;
    height: 100%;
    margin: 0px;
    padding: 0px;
    z-index: 0;
}

/* PHONE RESPONSIVE */ /* I HIGHLY suggest working from small screen up - instead of the larger screen and then putting in these overrides */
@media (max-width: 420px) {
    html body {
        overflow: hidden;
        height: 100vh;
        width: 100vw;
    }
    .container {
        z-index: 0;
        overflow: hidden;
        height: 100%;
        width: 100%;
        display: flex;
        flex-direction: column-reverse;
    }

    #map {
        z-index: 0;
        display: flex;
        height: 50%;
        width: 420px;
        overflow: hidden;
    }
    .left-container {
        display: flex;
        overflow: scroll;
        height: 50%;
        width: 100%;
    }

    .info-left-h1 {
        font-size: 10vw;
        position: relative;
        left: 20%;
        top: 100px;
        height: 10px;
    }

    .popup {
        display: none;
        position: fixed;
        left: 0px;
        height: 100%;
        width: 100%;
        z-index: 1;
        flex-direction: column;
    }

    .close-popup {
        font-size: 30px;
        margin-left: 100px;
        left: 60%;
    }

    .popup h1 {
        left: 0px;
        width: 100%;
        font-size: 10vw;
    }

    .popup input {
        position: relative;
        left: 0px;
        top: 200px;
        width: 100%;
    }

    .add-memory-button {
        position: relative;
        left: 100px;
        top: 40%;
    }

    .memory-container {
        width: 100%;
        height: 100%;
    }
}

/* TABLET RESPONSIVE */ /* I HIGHLY recommend not targeting devices like this - and instead just building up organically from small>medium>large etc -- and it'll be easier to write and maintain */

@media (min-device-width: 540px) and (max-device-width: 1024px) {
    html body {
        height: 100vh;
        width: 100vw;
        overflow: hidden;
    }

    .container {
        width: 100%;
        height: 100%;
        display: flex;
        flex-direction: column-reverse;
    }

    .left-container {
        width: 100%;
        height: 50%;
    }

    .info-left-h1 {
        font-size: 5vw;
    }

    .popup {
        width: 100%;
        height: 100%;
        left: 0px;
    }

    .popup h1 {
        font-size: 6vw;
        left: 0px;
    }

    .popup input {
        left: 12%;
    }
    .add-memory-button {
        left: 36%;
    }

    .close-popup {
        font-size: 60px;
        left: 90%;
    }
    #map {
        width: 100%;
        height: 50%;
    }
}

/* reset added in cog ^ */


/* SETUP */
* {
	box-sizing: border-box;
}


/* SETTINGS like variables and stuff */
html {
	--ink: black;
	--color: rgba(34, 193, 195, 1);
	--highlight: rgba(253, 187, 45, 1);
	--gradient: 
		linear-gradient(
			0deg,
			var(--color) 0%,
         var(--highlight) 100%
    );
	--neutral: #fddad4;
}	



/* STRUCTURE */
/* if you want to just take up the available space */
body {
	min-height: 100vh;
	display: flex;
	flex-direction: column;
}

body * {
	color: var(--ink); /* crazy idea */
}

main {
	flex-grow: 1; /* that'll stretch to fill the remaining space */
}

main {
	display: grid;
	grid-template-areas: 'center';
}

.map, .writing-area {
	grid-area: center;
}



/* TYPOGRAPHY */
.calm-voice, p {
	font-size: 1rem;
}
@media (min-width: 600px) {
	.calm-voice, p {
		font-size: 1.1rem;
	}
}

.loud-voice {
	font-size: 2rem;
}
@media (min-width: 600px) {
	.loud-voice {
		font-size: 3rem;
	}
}



/* STYLE */
.sidebar {
	padding: 20px;
	background: var(--gradient);
	--ink: white; /* just something to play with... */
}

main {
	--ink: var(--color);
}

.map {
	background-color: var(--neutral);
}

.writing-area {
	background-color: rgba(0,0,0,.5);
	padding: 30px;
	
	display: grid;
	place-items: center;
}

.writing-area form {
	display: grid;
	gap: 20px;
}

.writing-area form * {
	justify-self: start;
}

.writing-area form .form-field {
	display: grid;
	gap: 20px;
}

.writing-area form textarea {
	display: block;
	width: 100%; /* of parent... */
	resize: vertical; /* don't allow people to resize width */
}

/* any nessesary evils seperate */
.writing-area {
	position: relative;
}
.writing-area [data-action='close'] {
	position: absolute;
	top: 20px;
	right: 20px;
}


/* dev notes for you */
note::after {
	display: block;
	content: "I'm not sure how you want to do this. There are many ways... but on small screens - it'll depend on your header and layout space --- ";
	padding: 20px;
}


/* ITERATIONS */
.writing-area {
	opacity: 0;
	pointer-events: none;
}

body.modal-open .writing-area {
	opacity: 1;
	pointer-events: initial;
}



/* FIRST BREAK POINT */
@media (min-width: 700px) { /* or whatever works */

	body {
		display: grid;
		/* removes flex stuff */
		grid-template-columns: 300px auto;
	}
	
	note::after {
		content: "";
	}

}