@Branka-and-Silvia0 Yes, I would review them. But wait until you check with the neighbors as to whether they were a disturbance. If not, maybe something like "This very young group were polite on check-in and obviously did make an effort to clean up, however more than usual cleaning time was required after their stay, and evidence of many candles being used was cause for fire hazard concern." I'd also send them some private feedback, letting them know that it is not okay to burn candles in someone else's home, especially when it was obvious that they were drinking, so that they could have burned the place down, mention the broken sofa, stain on the wall, etc. and let them know that more mature behavior is expected from Airbnb guests. Personally I like to give young people a chance to understand what they did wrong and be afforded the opportunity to improve, unless the behavior is really bad, rather than just immature.
I hate people using candles- aside from the fire hazard, they end up dripping wax everywhere, which has to be scraped off floors and counters and if it drips on upholstery or rugs is almost impossible to remove. I plant candles in a container of sand- when they drip, it just goes into the sand, and if someone falls asleep with them lit, they will go out on their own once the flame melts the candle down to the sand.
I don't know that the fact that you found evidence of drinking could really be considered to be breaking your "no parties" rule unless the neighbors say there were many more people coming and going than the 7 booked guests. Seven 18 year olds are a party unto themselves. And 7 people of any age may drink together while staying- the issue is whether they were disturbing the neighbors, being super loud, blasting music, and invited unbooked guests.
I have to say, I don't think 18 should be considered old enough to book on Airbnb. While I know some 12 year olds who are far more mature and responsible than some 35 year olds, most 18 year olds, generally speaking, are pretty immature and clueless.