Are all of these sentences grammatically correct? And Which one sounds more natural?
I'm finishing working at 4I'm finishing to work at 4I'm finishing work at 4I'm going to finish working at 4I'm going to finish to work at 4I'm going to finish work at 4I'll be finishing working at 4I'll be finishing to work at 4I'll be finishing work at 4

Question

Answer

"I'm finishing work at 4" , "I'm going to finish work at 4", and "I'll be finishing work at 4" will all work depending on the tense your speaking in. You could also say "I finish work at 4".

Answer

I will finish work is more common and correcte 
You can say also I will finish work at 4, or i will be finished work at 4.