Hello 
Sometimes I struggle to finish a set of 8 reps in one shot (especially for shoulders and chest press). So I take short breaks ( about 10s ) and finish it in 4 -2 - 2 reps. In that case what should my feedback for the coach be ? I don’t want to say that it’s too heavy because i can lift the weights just fine, and in terms of performance I can do the reps in a proper way.
Is it ok to say that the weight is “ok” and the performance is “perfect” ?
Thank you
Hey George 
So although you might think you can lift this weight, the weight you’re trying to lift is really still too heavy for you in this scenario. Three seconds is around the ideal amount of time [to rest] between reps at the end of a set, and if you are consistently having to take short 10 to 15 seconds in such a case, you’re really not keeping your heart rate in the optimal zone, and defeats the purpose of the workout especially when you are doing 4 reps-10seconds rest-2 reps-10seconds rest-2reps.
The solution is really to use a lighter weight until you can perform the workout for 8 reps at a steady pace, so you should indicate that the weight was too heavy here 
Hope that’s clear!-it sounds like you’re putting in some super efforts so keep it up 
