Cannot add new themes

I have been struggling to get WordPress on my new site for several days. Finally I was able to get it installed through my cPanel, but now when I access the wp-admin, login in to my dashboard, and want to make changes, I cannot change the theme. I cannot upload any themes manually either.

If I press “add new” or the “+” button, it doesn’t pull up anything. The page is blank. I can click on all the different filters, but it still pulls up a blank page. It does the same thing for the plugins. If I click “plugins” from my dashboard, it takes me to the “customization” part of the website, and not the plugins list at all.

At this point, I am so frustrated. I do not understand what is going on or how to remedy it. Any help is greatly appreciated.

I am not sure what category this belongs in, but I have added a few different threads in the last year, which never get a response, so I am hoping I can get some kind of help. If there is a better, more responsive forum where I can get wordpress help, I would love to know about that as well! Thanks!