I have a question about using XP to aquire talents. The arbitrator starts the game with Basic weapon training SP. yet he has talent advances for it as well. If he takes those does it give you a bonus? like skill mastery? There are several ranks that allow the class to purchase it.. Thanks.

Hmm Ok or does it mean each time you take it you can choose a different weapont type..

Example Basic Weapon Training SP… the first time i take it i can get Combat shotgun. the 2nd time i take it I could take pump-action shotgun. etc etc.?

Basical no.

There are different Talent Groups

Basic, Pistol, Heavy…

Basic weapons are counted in Groups: Las, SP, Plasma etc.

So you have Basic Wepon Training Las you can use all Weapons which are listed as Basic Lasweapons, SP every Basic weapon which is listed under SP.

You can´t take Basic Weapons SP twice to get a bonus when using SP Weapons. Evertime you take this talent ist must be taken on another group.

The reason for these duplicate listings is because people can choose alternate background packages and alternate ranks which may not include these talents.

So a character which does not get this talent due to a special background package, can now still purchase the talent for XP along with other advances.

Which, ultimately means, is that if you already have the talent, there is absolutely no need to worry about taking it again. As Darth Smeg said, its there to future-proof against alternate character creation rules that don't give the weapon training.