How do I disable the blue function keys for my Vostro 3300?

I recently had a laptop repaired for my own use; the battery was replaced and it was looked over to see if there was any problem with the hard drive (there wasn't).

It was working perfectly fine for a few days, but now whenever I turn it on, I can't use any of the keys with the extra blue functions; I can't scroll up or down on ANYTHING because it defaults to increasing/reducing brightness and I can't type because 8 letters are numbers and symbols.

I have read a few solutions online and on here, but maybe I'm not doing them right because either I don't see the options or they straight up don't work.

It's getting real frustrating and I can't keep using the on-screen keyboard forever.