I have 16GB ram installed but only 5 is available?

Just curious as my uncle who's a tech expert says it's fine but it keeps bugging me that it's not like 12gb or something. The bios definitely detects the ram but many searches direct it to my intergraded graphics hogging it up but how do I fix this?

Edit: just no longer writing here as it's getting fixed free of charge tomorrow. Praying it gets better but rn I'm pretty depressed. Thanks for all your support guys, I tried every method and responded the best I can.

(SOLVED)