Re: Future Simple or Future Continuous
There is nothing wrong with your answer, other than there should be either a comma or a full stop after "it's OK" (and OK should be in upper case). There is no need to capitalise "file".
"I'll be seeing him later" is a little more colloquial and it's not necessarily a version I would teach students until they are at least upper intermediate. I would give "I'll see him later" or "I'm going to see him later".
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.