i keep loosing in the arena

Well your running 3 healers.. a low dps tanky attacker.. and an outdated dps; so when you call the assist with gs, the assister is already doing low damage.
There is many posts on this forum with good tips on who to farm for your arena team

I like Barriss heal but she doesn't do any damage. JC is allways the first to die. Should i keep Vader?

Develop you Boba and put him as lead and try for now:

* BF (L)
* GS
* Ahsoka
* Phasma
* Lumi or Bariss

Try to focus on a faction to have more synergies, you have a bit of all and you're wasting on resources. GS is really easy to gear up also and hit hard, especially under BF lead. Phasma will give you TM. Ahsoka also hits hard at your level. You should gain around 300 places.

That sounds good since they all are 6-7* Little bit of developing and they're good to go :)

Well maybe you should tighten things up.

(sorry, I had to)

EP leade, Vader and Boba is a good base for a team. Level them up abd add in RG as soon as you develop him more, and maybe Phasma, Rey etc. on the fifth spot.

Also: Keep your atena team at the highest possible level. I see your EP is level 74 and the second—highest is only 70.

Money is the problem for higher levels... Rey is almost getting her 6* . I'm suprised how good EP is. And I also realize that i really need to to do more damage and that's probabaly the reason for me to loose all the time

In your case i would focus on EP, Vader, TFP, Boba and RG (until shore trooper is available). Try EP, Vader, GS, Lumi and Boba, until you got the others leveled/geared.

I started developing Boba and his slowly getting his 7*. Thanks for all of you for good advices