Trying to make div move to another div - html

Question

So I am trying to make it look like this
However, it currently looks like this
As, you can see the top section with the logo and register have their own section. I want it to stay on top of the background image. I do not want to use position: absolute; or position : fixed; since i want it to say in its own section. I have also tried using a negative margin and it does not work. Any help is appreciated.
.top-firstsection {
display: flex;
}
.logo-header {
height: 80px;
}
.nav-list {
margin-left: auto;
list-style: none;
display: flex;
}
.leftandright {
display: flex;
justify-content: space-between;
}
.login {
font-family: Helvetica;
font-size: 13px;
color: #000000;
letter-spacing: 0.98px;
text-align: center;
text-decoration: none;
line-height: 26px;
cursor: pointer;
}
.register {
font-family: Helvetica;
font-size: 13px;
color: #0972D7;
letter-spacing: 0.98px;
text-align: center;
text-decoration: none;
line-height: 26px;
}
.first-left {
padding-top: 220px;
padding-left: 171px;
}
.first-left h1 {
font-family: Poppins-Regular;
font-size: 40px;
color: #000000;
letter-spacing: 0;
line-height: 50px;
}
.sectionOne-textbox {
border: 1px solid #EBEBEB;
border-radius: 4px;
font-family: Helvetica;
font-size: 14px;
color: #000000;
letter-spacing: 1.05px;
line-height: 52px;
width: 80%;
}
.sectionOne-button {
background: #1F8FFB;
border-radius: 4px;
border: 1px solid;
padding: 16px 25px;
font-family: Helvetica;
font-size: 13px;
color: #FFFFFF;
letter-spacing: 1.3px;
text-align: center;
margin-top: 24px;
}
<section class="first-section">
<div class="top-firstsection">
<img src="logo.svg" alt="logo" class="logo-header">
<ul class="nav-list flex">
<li>
LOGIN
</li>
<li>
REGISTER
</li>
</ul>
</div>
<div class="leftandright">
<div class="first-left">
<h1>Open marketplace <br> for ordering & purhasing <br> scientific experiments</h1>
<input type="text" id="" class="sectionOne-textbox" placeholder="Discover new experiments...">
<button class="sectionOne-button">GET STARTED NOW!</button>
</div>
<div class="first-right">
<img src="firstsectionbackground.png" alt="main graphic" class="main-graphic">
</div>
</div>
</section>