I find that with some weapons and armor that i cant upgrade them to ledgendary ive heard that you have to get better in smithing from what you previously had from upgrading it to make it better. (im 100 smithing) is this true because it seems nearly impossible to do if u have 100 smithing unless you have potions or enchantments. Is it meant to be like this or should it be fixed?

you have to have the appropriate smith perk also to get it to legendary. without the perk it would take a smith skill of 190+ to get a item to legendary. with the perk you need a level 91 skill.

how do u upgrade weapons to ledgendary then ive got the arcane blacksmith perk

Arcane blacksmith perk doesn't offer the 2X smith rate the other perks do.

With 100 smithing, the arcane perk, and 1 item that gave +20% smith, and 2 items with +15% bonus I was only able to get to epic.