SOURCE

<div style="height:100vh">
    <div class="top">

    </div>
    <div class="bottom">
        <div class="garn">
            <div class="parent">
                <div class="elementDiv1">11222</div>
                <div class="elementDiv">
                    cesces
                </div>
            </div>
        </div>
    </div>
</div>

.top{
    height: 300px;
    background:red;
}
.bottom{
    height: calc(100% - 400px);
    background:'blue'
}
.garn{
    height: 85%;
    background:'yellow'
}
.parent{
    height: 100%;
    overflow: scroll;
    background: pink;
}
.elementDiv{
    height: 600px;
}