Update- I redesigned the menu so there is no problem with it now.
I’ve since switched to the child theme and filled in the footer manually; I saw that it was erased by the main theme. It’s working fine now with the child theme.
It seems that there was a bug that if the blog post navigation is turned off, the footer will be wiped out as well. This is what happened on my site, I don’t know if other people experienced the same.
After discovering these, the site is working fine now on the mobile and desktop. Thank you for your time.