Sd ok (?) what about rest

Apparently the new photos and videos are being saved to sd but I still cannot move the previous, or screenshots, or anything else except maybe ebooks. I am also unable to download apps, at least working versions, and/or move them. At least some are now showing more than 0 bytes, but it doesn't do much good if I can't install and use them. I recently tried with X-plore, 7.50 mb downloaded November 14, and it says "app not installed". I'm not sure if I can afford to have this checked out at some fancy repair shop, or if that would even help. Why can't there be just some 24/7 number to call real people who actually speak English, are not reading from a script, and actually know a thing or two about these problems?