Nevermind it seams to be a mod,as a clean non-moded game works fine.

When loging into hosted multiplayer the inventory resets to all the stuff that you start with, all other items dissapear. It does not happen in single-player.

well nm I started a new game and the tin smelting was there.
no idea what I did

actually the whole tin tree is missing

nope that's nickel

I have 2 problems
1 Tin ingots are missing from tech tree
2 Bronze smelting is unresearchable