The blocks of the second line take the width of the blocks of the first line, how to fix it?

Question

Bootstrap

There is a line of two col-6 blocks and a term of three col-4, when the screen is reduced, everything goes right, but at a certain moment, when the blocks should stand one per line, the blocks of the second line become the width of the blocks of the first line and because of this it moves out block content.

Первая строка:
 <div class="row justify-content-center text-center">
        <div class="col-lg-6 col-12 mt-5"> 
        </div>
        <div class="col-lg-6 col-12 mt-5">
         </div>
</div>
Вторая строка: 
<div class="row justify-content-between text-center">
        <div class="col-lg-4 col-md-6 col-12 mt-5">
        </div>
        <div class="col-lg-4 col-md-6 col-12 mt-5">
        </div>
        <div class="col-lg-4 col-md-6 col-12 mt-5">
        </div>
</div>

Answer 1

remove col-md-6