Header and Entry Title Margins

Hi everyone,

First time poster so apologies if I’m posting this in an incorrect place.

I’m new to making my website, and quite compute illiterate, so I had a couple questions about margins. Here’s an example of one of my pages: https://iiingela.com/online/

How do I get it so that there’s not that gap at the top of the page before my name appears? Also, is there a way to close the gap below the header but above where the title of the page is? AKA, is there a way to move up the word ONLINE so that there’s less of a space between that and the white line of the header?

Let me know if I need to clarify at all.
Thanks in advance!