How about some small encounter with a curse for someone who wants to take every opportunity they have to get an item. My master noticed that i like to rob people every possible opportunity even if it actually dangerous and can be super blant. So he gave enemies some magic that hits robbers, gave me cursed sword and made quest where robbing someone showed that they are actually victims who needs help.
Use players behaviour as a key to move plot and via story let them learn that their actions might be harmful.
Lets say, you can give him some herbs and he eats it, but turns out he ate something that was corrupted so now he has diarrhea in the middle of the fight, or he grabbed a sword out of the stone and now suddenly everyone wants him to fight some dude who is bigger, stronger and calls himself Arthur The Cursed King. Or it might be that by interrupting someone, they decide to not give party some presents they supposed to give or give him not exactly what he wanted or just change topic of discussion into something stupidly long and boring like “frog guy starts a long story from two decades ago about some hidden treasure here in the swamps” but that actually leads to nowhere and just spends time
Gosh, you can even make a quest to get a bear but talk about it like “i heard, there might be a bear seller in next town” and say in the next town something like “oh, he was here yesterday but you came too late, he is already left”. Encourage him thinking he might be loosing some great experience and fun because of spending time on things.
Btw, you can actually give him a bear. A small one. That needs protection and help. And make him spend his actions on care for his pet.
Don’t know german, still enjoying the hell out of ich_erl