I recently got into speedrunning and didnt expect to get a top 50 score glitchless could I still submit or do I need to keep grinding while filming

What do you expect to submit if you have no proof of your result. Also Glitchless has 52 submissions, so top 50 time doesn't sound particularly difficult to replicate :D Please, try again and submit a video recording.

could you theoreticly proov when still got the charakter files ore any other thing that could proove it

Yes, you can prove it by having a video of you completing the run!

(Character files aren't proof because you could easily just cheat in a run and nobody would know)