How to get my software into Ubuntu?
may somebody tell me how i can add a freeware to the ubuntu software-center?
Use http://myapps.developer.ubuntu.com. You upload the source code, decide a license and optionally a price. Then people review your code and it'll be added to the software center for people to download it. There are some requirements, such as it needs to be installable in /opt.
In order for a piece of software to be included in Ubuntu, it must meet the Ubuntu License Policy.
You can find details on how to request software be added to the Ubuntu software centre on the New Package page of the Ubuntu Wiki.