.collapse.show {
    display: block;
}

.collapse.show {
    display: flex;
}

Hi,

Could you try something like this?

<div class="row" id="collapse"> 
 <div class="col-md-6">
 <div class="form-group ">
 <label class="" for="">input1</label>
 <input type="text" class="form-control" name="" id="" value="">
 </div></div>
 <div class="col-md-6">
 <div class="form-group ">
 <label class="" for="">input2</label>
 <input type="text" class="form-control" name="" id="" value="">
 </div></div>
 
 
</div>

Let me know if that is what you are looking for... otherwise please expand your question.

Thanks