fuck if I know

as you know

as it is already known.

fuck it

An expression of great indifference or nonchalance.

fuck knows

I don't know; nobody knows; it is unclear.

fuck off

To go to hell; to disappear or go away; to screw oneself.

fuck someone upside down

To give someone a bad scolding.

fuck someone's brains out

To sexually penetrate (or be penetrated) in a vigorous but pleasurable manner.

fuck this

A dismissive expression of great indifference or nonchalance.

fuck with

To interact with in a careless or inappropriate way.