Yes, it's all i needed! Thanks a lot!
Grade != submission, what a poor mistake. But before file feedback I did this for PDF feedback and as i saw, PDF feedback is stored in submission table, while File feedback is stored in grade table, so for PDF was working, but for File not. Iam crazy of that moodle database and tables, I still don't understand to that.
Anyway I want thanks to you for quick and very helpfully advice, you are great!