Oil on valve cover and snoring

Moin, I’ve been having little problems with my moose lately. He’s just got the 100′ down and “fastened” a bit strange when giving gas. Sounds like a quiet bug engine, that’s what’s really best. Was in the workshop, only that’s so quiet in the interior, that the master didn’t hear that because of slight hearing damage. But for safety, the engine cover has been unscrewed, not the clattered one, and see there: full of oil the thing. Master thought it might be that the vent hose that goes in there is leaking, but that’s something you have to check out more. Does anyone know the problems? That with the oil I’m worried about, I think that something is loose, it’s getting stronger and weaker, partly it’s also gone… Solemn