Playing by yourself is one heck of a challenge, but we love a challenge, do we not? The hardest part about the Blackforest is trying to find the surtling cores that makes the kiln and smelter. Run around and try to find a burial chamber, and then mark it. You can run from trolls because they are slow. You can run from everything in the Blackforest. Once you find one of these burial chambers, your next step is going to be the hardest—trying to get the cores out of the dungeon. You're going to need 5 of them to start forging bronze. Bring the best food, armor, shield, and club with you. It's tricky but also bring a campfire, because you can place campfires in the right spots and use them as a defensive weapon. The best way to get good at Valheim is practice, and you will probably die a lot until you learn and study how the enemy moves and attacks.
After you get the cores and smelt a little bronze, I highly recommend forgetting about armor for a second and build the bronze axe and a boat. The bronze axe should always be the first tool you make, because now you can chop every tree in Valheim. The birch trees will allow you to make furniture, and more importantly, the Finewood bow. With this bow upgrade, some fire arrows, and your house looking more comfortable, you should have no problem taking on trolls.