where can you get the regeneration technique? I played through this game already and I dont know where it is.

You can learn it from Kan, the leader of the orcs in Faring (you need to get a high enough rep with the orcs before you can see him). You can also learn it from King Rhobar if you choose to side with Innos towards the end of the game.

Kan in Faring or king Rhobart in Vengard
i hope that are also their names in other languages. (orc leader respectively king of myrthana)

it requires 300 strength.

both teachers also want some quests solved/fame:
Kan - faring fame >= 75, orcs fame >= 75, "destroy last tresistance of morras" succeeded
Rhobar - "for innos" succeeded

ps: i have no idea how the quests are called in the english version, i just tried to translate the name.

Euh.. I mean in gothic 1, I would never play G3 again. but thanks anyway.

Regeneration doesn't exist in G1 nor G2 unfortunately. Kind of annoying, but by the end of the game you'll find yourself with a lot more potions and herbs you'll ever need.

in standard gothic is no regeneration skill.
you're probably playing a modification.

Evidently a bug in the Unofficial Gothic patch