I used the flexbox layout technique for this challenge.

Hey D'émils Dingui, well done!

You just need a little tweak to your layout. Instead of making the whole card a flex, better to make the subscription and why-us sections in a container class called .card-body.

.card {
    max-width: 635px;
    margin: 0 auto;
}

.card-body{
    display: flex;
}

.subscription, .why-us {
    flex: 50%;
}

And then on mobile breakpoint, change these parts;

.card{
    padding: 5rem 2rem;
}

.subscription, .why-us {
    flex: 100%;
}

Overall, you did great.