As long as you have good form slow is better. But its also alot more difficult.

Can you do slow pull ups?

I'm hearing many good things about negative reps. and lowering the weight very slow.

I like to do light dumbell flys and go very slow all the way down, even when using
20-25lb dumbells my chest is sore for a couple days. I also do partial flys halfway
up them back down to keep constant tension on the pecs.

Its actually good to do it slowly and controlled and feel the stretch. Instead of rushing through the set.

yes there is such a thing, I was always too slow with it all, I don't think there's any better or worse, just follow your ways, listen to the trainer of course but most importantly listen to yourself

Most is timed