Quests involves him repairing stuff, finding people he wants, finding stuff he wants, getting on his good side to get him to upgrade your weapons.
Help Garun Get Caught Up, He's always busy trying to maintain the tribe's weapons, and if you could help him get ahead a bit he'd really appreciate it. The results are based on the extent of your skill.
Get Garun some Damn Tools, if he wasn't working with such primitive tools, he'd be able to do his work a lot faster. Make or find him some decent pliers, clamps, and such and give or trade them to him. Two multitools should do it.