The McFit in Trier Nord is awesome.
The staff are very…read morefriendly, the gym is always clean and has a great community vibe.
I've been going to this gym a few times a week for 6 months now and love it.
I should also add I don't speak much German, and but the staff knew enough English to show me around the first time.
The gym has pretty much everything you would expect at a big box gym. And the price is very good. (Approx 25€ a month.)
The only downside is that sometimes some of the lockers locking mechanism is broken, so you just need to check the locker before putting your stuff in.