Why is w-80 class not working in bootstrap?

I need to put horizontally centered div on the bottom of parent div. Centered div needs to have 80% width of a parent. This div also has a sibling in form of < img >

<div class="position-relative w-100">
     <img class="w-100 mt-3" src="..\assets\images\bg_choice.jpg" alt="bg_choice">
     <div class="p-md-2 p-lg-4 position-absolute bottom-0 start-50 translate-middle-x transparent-background text-center" style="width:80%; font-size: 2em;">
          Text in the middle of centered div
     </div>
</div>

This is so far what I've got, however I would like to use w-80 class but it's not working. I guess it has to do with position absolute. I have tried using position relative but I still don't know what is wrong.