I know loading screens and the intro cutscene does not count in the speed run. but what counts as a loading screen. do I stop the timer when I enter the elevator? Because there are a few seconds in the elevator before it cut to the loading screen. also after the loading screen when the next level is popping in there is a few seconds of black do I restart the timer when the picture comes back?

Which platform are you running on? If you run on PC you should use either the in-game timer or run your livesplit with the autosplitter. On console it will be retimed anyway, but the best I can suggest is, if you still want splits, pause when you see it say loading and unpause when you see the floppy disc saving icon in the buttom right. It is possible to move while the screen is black.

I'm on PS4. I got the trophy for doing a run under 35 mins. but when I counted my time I realized I had a 32:47. good enough for 4th place on the PS4 board and I just need to shave 1 min off and I'll have 3rd place.

So you're saying if I submit a run for PS4 the verifier will time it for me?

Seeing as there is no in-game timer, we manually remove load times, yes. That's why you only see precision in seconds.