The first sentence is correct grammatically, but your punctuation is not correct. The best form of the sentence is: Thank you very much, Mr. Smith. I appreciate your time helping me correct the project. A comma by itself is not strong enough to connect two independent clauses. You must use a period or semicolon, or you have to add in a conjunction following the comma (for, and, nor, but, or, yet, so).

Hi Javi, The first example you wrote (with a few edits) is the correct one, "Thank you very much, Mr. Smith. I appreciate your time in helping me correct the project." In these examples, "correct" is used as a verb. Thus, the second one isn't correct, because "correction" can never be a verb. As for the third, "helping" is already in the continuous form, so "correct" should not be. I hope this answer helps. Please let me know if I didn't explain clearly.