3 column card

First i would highly recommend you to center the body to make things easier for this i would highly recommend doing:

body{
display: grid;
min-height: 100vh;
place-content: center;
}

Then on your container make the whole thing with a width wich on your case would be:

.parent-div{
width: 350px; /* note that this width can be any width you want */
height: 550px; /*note that this height can be any height you want */

This are a few documents that i would highly recommend to anyone, i still look at them whenever i'm kinda lost.

Learn Flexbox

Centering in CSS

Just a few things I noticed:

1. Try increasing the padding on your .parent-div div{} Perhaps try starting at 30px and go from there.

2. The button width is way too large and the height isn't tall enough.

3. The button margin from the paragraph needs to be longer.

Sidenote: If you are familiar with Grid, you could easily space all of your elements out vertically.

It looks really good other than those few items! Great Job and Keep Going!