1. Did i understand it right, that Ad Agency will come in a 1.5.x version soon?
Hi,
Yes, as you can
see here, we are still working on this extension.
2. Does it work as a component on my Joomla site (1.5.5)
No yet, but soon.

3. Untill it comes in a 1.5.x version, can i then purchase it in the 1.0.x version, and get it afterwords in the 1.5.x version and implementate it in my site.
You can purchase iJoomla Ad Agency for J! 1.0 and once we release the J! 1.5 version you will get it for free.
I gues i have to install 1.0.x on a subdomain for my advetisers right? And that they from there can manage their campains on my 1.5.x site?
Yes.

Also i would like to know if it is possible to make some sort of pre set. Like fx. that google adds is pre set, until an adviticer change it with his campain? Hope you know what i mean....
I´m not sure what do you mean with this.
Why don´t you make it possible to create our own pakkages in your store??
Why don´t anyone respond to my quistions???
On weekends the responses can be delayed.
Let me know if you have more questions about this extension.
Best regards,