Make sure to get high stamina and good health food items, get the best arrows you can at this stage, fire arrows and I believe you can make bronze by now? The finewood bow is a good one, upgrade it to the highest level you can. I never did the fire cheese for The Elder, just bow & arrow. You can avoid all the summoned roots easily by running to the other side and the pillars are enough to dodge the direct attack he shoots at you. You can combine it with placing some fires around if you wish. The only problem is crafting fire arrows I think, but in burial chambers you can get fire arrows too. There might be other ways but I haven't played this game for a while now haha
Not a Server, Its singleplayer - If I was to open a server I dunno if it'd be worth making it modded, so much can go wrong in a short time. However I am not opposed to opening a valheim server.