However do i disable function keys?

you May want to check in your Bios screen, other wise I do not believe there is a real route to shut them off.

My recommendation would be call dell and ask them.

You may also have to use an surface keyboard.

If all else fails newly get out a Big hammer, set the computer on some concrete and swing hard in a downward motion onto the computer. That's guaranteed to fix the function keys to where they will never come on again,