I alredy used search and found something, but the thread wasn't realy finished....
so, can I add a second hero to e.g the republic so that obi wan and windou can be used as hero?

no, its impossible to have more than one proper hero per side.

Is it possible to make a unit which the AI doesn't play?
so you can maybe make sth like a hero... (for having 2)

EDIT
Is it possible to make a unit which can't be played by the AI, and if yes how?

i think using the lua could work for that.

look at the numbers which are after the odf names of your "heros" in the lua under the team section and then set the numbers to 0. As long as you don't have ubermode on then this will most likely work. if you post your lua i could show u what i am talking about.

my rambling nonsense about why i say most likely

Yes it is just go to your lua and look for a line like this:

soldier = { "rep_inf_ep3_rifleman",9, 25},

I dont know which unit you want not to be played by bots but for example if you dont want this unit I posted to be played by bots let it look like this:

soldier = { "rep_inf_ep3_rifleman",0, 0},

Try it out!

this was also answered in your thread about having two heros if u want a bit of extra information.

sry for that in the other tread .
I thought I made an new topic about this but i made a reply

Your two original topics were merged because they were related. Obviously, you couldn't have a second hero unit, so you then asked about using a unit that the AI cannot play as with intentions of using it as a substitute for the not-possible second hero unit, yes? Merged again.