My banner picture isn't working as I wish

Hey guys. I’m new here, it’s my first post and as I’m Brazilian and English is not my native language, although I really like it and have lived in the USA for a while, forgive my English mistakes.

I inserted an image into my “banner image” on the first page and when I click to see what it looks like, it enlarges in a way that doesn’t satisfy me. There is a woman in the photo and the more I stretch the browser window, the woman’s face disappears. Is there a way to fix this? Any special settings for photos? Is it correct to say that they have to be PNG and with a 3:2 aspect ratio?

Guys, I just discovered that there is something called a “focal point” which you can drag and place where you want the focus of the photo to be permanent and I think that did the trick, I think…