How to style cards in css - html

Question

So I have this 2 cards aligned the way i want whit bootstrap and display: flex;. When i try to do some some changes in CSS like moving the details class in middle, or to change the width and height of the card etc it won't work. How can i do it ? Here is the code:
<div class="row">
<div class="col-lg-4 col-md-6 pop-up">
<div class="front">
<div>
<img class="girlimg" src="girl.jpg" alt="asdasda" />
<h2 class="activname">Guided hiking tours</h2>
<button class="activbutt" type="button" name="button">
SEE DETAILS
</button>
</div>
<div class="details">
<div class="duration">
<i class="fas fa-clock">Duration</i>
</div>
<div class="people">
<i class="fas fa-user-friends"></i><br />
<p>Max adults:10</p>
</div>
<div class="kids">
<i class="fas fa-child"></i><br />
<p>Max children:3</p>
</div>
</div>
</div>
</div>
</div>
<br />
<div class="col-lg-4 col-md-6 pop-up-2">
<div class="front">
<div>
<img class="girlimg" src="bike.jpg" alt="asdasda" />
<h2 class="activname">Rent a bike(4 hours)</h2>
<button class="activbutt" type="button" name="button">
SEE DETAILS
</button>
</div>
<div class="details">
<div class="duration">
<i class="fas fa-clock">Duration
<p>QUARTER DAY</p> </i>
</div>
<div class="people">
<i class="fas fa-user-friends"></i><br />
<p>Max adults:9</p>
</div>
<div class="kids">
<i class="fas fa-child"></i><br />
<p>Max children:0</p>
</div>
</div>
</div>
</div>
</div>
</div>

Answer 1

I think you should use the card class from bootstrap. https://getbootstrap.com/docs/4.0/components/card/. Then you will be able to change the default width & height of the card by overriding it from custom CSS.