Hey! Can you please tell me where I can read or watch a video about correct breathing during exercise? in most of the exercises I am able to breathe comfortably, and in some I am not. thanks!
Hey Aleksandr 
First of all let me give you a huge welcome 
There isn’t currently anything in the exercise videos or instruction cues for this, but it is something that we are currently exploring and I think we should expect to see something regarding cues for breathing in the future 
Instructions of exercises are usually fine, but it would actually be nice to include suggestions on when to inhale and to exhale 
Hi both, the standard general technique that applies to most exercises is to exhale on the effort/concentric part of the exercise (e.g. pushing up in the push-up, raising legs in leg raises) and inhaling in the easy/eccentric part (e.g. going down in push-up, lowering legs in leg raises).
Based on @alexpvp 's wording, I guess that perhaps he is referring to some dynamic and fast-paced exercises like burpees, where it is a bit trickier. I attach an article on Freeletics blog with more details:
https://www.freeletics.com/en/blog/posts/breathing-essentials-for-athletes/