remove margin between menu and title, also center logo

Hi, I know there’s about hundred posts about this issue and I read them all but none of the solutions worked for me, I don’t understand how css and html work and I’m new to all of this!

I tried adding the codes to the global css in the theme settings, but that didn’t change anything!
my website is Unholy Music

I don’t have a child theme (didn’t know how to add one yet), would anyone help me fix this issue?
also, it would be awesome if someone helps me center my logo and footer text, I’ve also tried hundred of codes to the header and footer areas in the theme settings but none of that worked as well, I’m not saying they don’t work, it’s probably me who didn’t know how to put them right

Appreciates it