What is the difference between be off work and get off work? Thank you very much.

That's a good question! I hope I can answer it well...

I think the difference is very slight. "Be off work" sounds like a state of being to me, while "Get off work" sounds like an action. Here are some comparisons:

A) "I was off work when she called me." = I was not at work when she called.
B) "I got off work when she called me." = I was at work when she called, but after she called I stopped working and left the office.

A) "I got off work to go back home." <- sounds like a normal routine, you stopped work and went back home
B) "I was off work to go back home." <- sounds like are describing why you took time off from your job (for example, maybe you took a week of vacation to go back to your hometown)

Got it. Thank you very much.