This is a super common Git authentication issue! I have to do some googling everytime I go through this process myself, it's kind of annoying...
But I just realized since it's an authentication problem, using SSH instead of HTTP might help (not sure if mentioning SSH will confuse you even more; I hope not).
https://github.com/ekzyis/repo
, I usegit@github.com:ekzyis/repo
after I added my SSH public key to my Github account (which I only had to do once).