Hi Andri, congrats on finishing your latest project.
To center your card, you can use absolute positioning. To try it out, add the following css lines to your container class:
position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%);
If you try your website on smaller screens, you will notice that it overflows, for better responsiveness, you can:
1 - use the rem unit instead of px.
Each rem equals 16px by default, to avoid impossible rem to px calculations, you can set the font-size of your <html> element to 62.5% which is the result of 10[px] * 1[rem] / 16[px], this will make each rem equal to 10px.
2 - use media queries
Good luck!