If you're going for the 2nd boss you should already have troll armor or bronze armor (go troll armor, more mobility, barely less armor, way less grind) plus bronze weapons and a fine wood bow. You should be able to avoid getting into melee range with any troll and take them down with arrows. You also have the ability to make portals and you certainly shouldn't be using a raft but a karve. Food wise you should be well stocked on carrot soup and meats (from setting up a farm and boar pen), various potions, and even one of the best foods in the game currently, serpent stew. These are all things accessible with just the first 2 biomes.
If you haven't done all of this you are indeed under geared, which is still entirely doable by a skilled player, but definitely not suggested if you are still struggling against trolls.
Valheim is very much a game where you are rewarded for patience and work with a much easier experience, and not meant to be rushed through.