3-column-preview-card-component-main using vanilla css and flex box

I managed to finish this in under an hour, however for some reason I feel like I have missed something since I was able to finish this quickly. From my initial estimate, I did think I would finish in less than 1 hour, but gave myself a bit of extra time in case. I forgot to put the animation for the button (which was next to nothing) in the estimate so I have to learn to look at the individual elements more closely as things like this could take more time depending on complexity.

For some reason I couldn't get the font for the h1 to show on the site, either I have missed something or I have something overwriting it in the css. With practice I want to get faster at creating such components, however I also want to write cleaner code as well.

Looking forward to any feedback.