resolution stuck at 30HZ

So I have a 50in 4k TV and a 27in 1440p monitor connected to a Dell optiplex 3040 running Windows 10 ( I am using it to stream games from my gaming PC) I am able to run the monitor at 60hz 1440p but when I use the TV at anything above 1080p I only get 30hz, now its important to know that my...

So when trying to copy across HDD's or external devices my explorer.exe resets aka closes and repoens (my deskstop and task bar etc goes away and comes back) for example, when trying to move a file from my 2nd hdd to my first my dekstop and taskbar goes away and comes back and nothing happens no...