How do i make a gradient for stuff on my layout

Here is a cool website to make css gradients :)

I meant the top bar and other stuff, not the background

you can use that website to generate the gradient you want
for example if you want to change the top, you can do that:
nav .top { background: linear-gradient(90deg, rgba(2,0,36,1) 0%, rgba(35,35,164,1) 35%, rgba(0,212,255,1) 100%); }
ofc its an example with the default blue gradient from that website