không biết gì hết 
to not know anything at all [ không ] : (1) no, not; (question tag); (2) air; (3) empty
[ biết ] : to know, know how to do (something) be aware of
[ gì ] : what
[ hết ] : finished, exhausted, finish, exhaust; completely, totally, all, of all, everything
Most Common Compounds Set 1:
Most Common Compounds Set 2 :