CSS span or p goes outside of div - css

Question

I am trying to replicate stackoverflow-like design and ran into problem.
<div class="flex-grow-0 pd-around-m"> # line 1
<div class="flex-col fill-row mr-around-s"> # line 2
<div class="flex-row fill-row"> # line 3
<div class="flex-col justify-center mr-around-m"> # line 4
//Buttons
</div>
<span>
//Long Text!!
</span>
</div>
<div class="answer-bottom"></div>
</div>
</div>
.fill-row {
width: 100%
}
.flex-col {
display: flex;
flex-direction: column;
}
.flex-row {
display: flex;
flex-direction: row;
}
.mr-around-m {
margin: 1rem;
}
.justify-center {
justify-content: center;
}
When I enter long text in <span>, <div> in line 2, line 3 goes out of div box in line 1.
I tried adding white-space: pre-line to div in line 2 and directly at span but still text goes out of the box.
How can I keep the text inside parent div?
navigation bar on the left has property width:20% but gets squashed. Is this because of the textbox problem I asked above?
EDIT
https://jsfiddle.net/pzcu2yjn/
Here's a replication of my problem. if you make the text in span short enough, navbar and menu will have some empty space in the left maintaining 20% of the screen. however, if you leave the long text as it is, it gets squashed and 20% gets ignored

Answer 1

Few things:
On using flex it is good to provide width for left and right container since container will not know what it should when content increases.
Once you have the width assigned to the right container that is when you can use wrap functionality so the wrap works only for right container and it doesn't have no impact on less container. overflow-break-word;
NOTE:
I have removed unwanted code from the code, you can put it back it has no impact if those are needed.
.flex-row {
display: flex;
width: 100%;
}
.navbar {
display: flex;
flex-direction: column;
justify-content: flex-start;
border-right: 0.05rem solid var(--main-border-color);
align-items: flex-end;
width: 20%;
border: 1px solid red;
}
.pd-around-m {
width: 80%;
border: 1px solid blue;
display: inline-block;
overflow-wrap: break-word;
}
<div class="flex-row">
<div class="navbar">
<div>
menu1
</div>
</div>
<div class="flex-grow-0 pd-around-m">
<div class="flex-col fill-row mr-around-s">
<div class="fill-row">
<span>
AaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaaAaaaaaaaaaaaaaaaaaa
</span>
</div>
<div class="answer-bottom"></div>
</div>
</div>
</div>

Answer 2

You can add overflow: hidden; to prevent the text from going outside of your div.
There's a very similar question with a precise answer:
<span> element going outside of <div> element