Make sure you are well fed, 3 foods. at that level cooked meat/grilled neck tail, berries, mushrooms, honey are your options. Honey has the best health regen by far so good for boss fights.
Make sure you have your resting buff at all times as it increases xp gain, health and stamina regen. If you need to refresh it on the go just build a campfire and sit next to it (x) for 30 seconds to get the 8 min base buff back. Always start a boss fight in the morning, fighting at night is a mistake due to the cold debuff and more enemies around.
Remember there is no rush and its easy enough to avoid the first bosses attacks if you need to regen health or stamina, just keep a big rock or two between you and him.
Either a bow or a melee weapon will do, he's just the training wheels boss fight.
Valheim is very much a game that rewards careful preparation and punishes rushing into things, so take your time to gear up and all and things are a cakewalk.