i hate those intro little movies, takes an eternity. can i delete them or this is considered modding the game and all that stuff?

Short answer: you can remove them, but there's a catch.

If you end up restarting the game during the run (e.g. the game crashes or something), the intro videos are part of the game and are expected to be present, so not having them would invalidate your run in that case.

This is only enforced in cases where they would affect the time of the run, and most people reset when their game crashes anyway, and this game has no strats that would require a restart, so it's usually fine.