Messed constrains and material after linking

Hey guys
I linked a character from another blend file into a scene for animation. I already did all materials and constrains in the orgininal blend file but I can’t really use them with the linked version.
Everytime I reopen the file I have to change my matrials because there are no textures chosen.
My constrain for a rotating wheel doesn’t work anymore.
It really makes me crazy to redo many settings every day.
Whats the best way to link or append a character to another file? Do I have to do anything after linking? Import the textures or something like that.
If this is normal behavior after linking the feature would be really useless in my eyes ^^