Is there any advice to stop my boyfriend from snoring?

Few things: Things that can help: avoid sleeping on back, weight loss, treatment of any nasal congestion (nose spray or breath right strips) and avoidance of alcohol. After that there are other things to look at such as is there a medical reason such as apnea or structural problem with nose and mouth.

Sure: You can try simple things like have him sleep on this side (the sell sleep shirts that have tennis balls on the back), avoid alcohol or sedatives near bedtime, and lose weight. If a robust snorer, you might consider having a sleep study to determine if he has sleep apnea, which can be much more serious problem. Also have his md check his throat and tonsils for any airway obstructions.