Alisson, I recommend studying the Grid system that you should follow when using bootstrap.
link
By declaring your HTML by following this structure, your screens will be able to adjust according to the size of the device you are accessing.
A simple example:
Here, I want to for small screens, my button occupy the entire screen. For large screens, only 1/4 of the screen:
<div class='row'>
<div class='col-lg-3 col-xs-12'>
<button type='button' class='btn btn-primary' style='width:100%'>Botão 1 </button>
</div>
<div class='col-lg-3 col-xs-12'>
<button type='button' class='btn btn-primary' style='width:100%'>Botão 2 </button>
</div>
<div class='col-lg-3 col-xs-12'>
<button type='button' class='btn btn-primary' style='width:100%'>Botão 3 </button>
</div>
<div class='col-lg-3 col-xs-12'>
<button type='button' class='btn btn-primary' style='width:100%'> Botão 4 </button>
</div>
</div>
Remembering that you should never change the position of your page elements by using CSS styles like position: absolute and top / left fixed. This will produce a distorted effect when used in conjunction with the bootstrap.