how do you help a friend grow or self-improve?

well, first they have to realise theyre wrong. if they arent aware of mistakes theyve made, try to talk to them ab that first. it depends on what they need to grow and improve upon, but having just one friend confront them gently about it should definitely help

tell them your worries about them, and tell them that youd like to help them improve. if they make you uncomfortable or others, then set boundaries with them. if they hurt themselves with their actions, tell them that you notice certain patterns in the things they do that end up getting themselves hurt. after all this, see how they respond. you need to make sure you DONT hurt their feelings or else theyll just end up angry instead of responsive. make sure to set CLEAR rules/boundaries/etc so that they understand. hope this helps at least a little, but its hard to help when idk what the issue is exactly.