Thanks Rahman for the reply,
i tried but it did not worked. If i start CC i get directly the same problem. Same with install.app for cs6. I also tried this in another network from my friend. 
Hi StefanHeg,
Follow the below steps for Download Error under Apps tab,
1. Open Activity Monitor from the Utilities folder under Applications.
2. Check for Adobe processes such as Adobe Crash Daemon, Adobe CEF Helper, Coresync, Creative cloud, If you find them Force quit it.
3. Open the finder window and press Command + Shift + G button.
It will open the Go to folder search box, in that type ~/Library and then click on Go.
Then, go to Application Support/Adobe folder and delete the AAMUpdater and OOBE folders.
4. Now, open the Go to folder search box again, in that type /library this time and then click on Go.
Notice that this time it is just /Library and the ~ symbol is not included.
Then, go to Application Support/Adobe folder and delete the AAMUpdater, Adobe Application Manager and OOBE folders.
5. Now, open the finder window and Press Command + Shift + U button.
It will open the Utilities folder, from there delete the Adobe Application Manager and Adobe Creative Cloud folder.
6. Now, run the cleaner tool from the below link. Do not click Clean All button.
Use the CC Cleaner Tool to solve installation problems | CC, CS3-CS6
In the cleaner tool, check if you have Adobe Creative Cloud or Adobe Application Manager listed, If found select it and click on Clean Up Selected button.
If not found, close the cleaner tool.
7. Download and Install the Creative Cloud Desktop from here : Free Creative Cloud | Download Adobe Creative Cloud free trial
Launch the Adobe Creative Cloud from Applications folder > Sign in and click on Apps tab.
If you still face the same issue, please try enabing the Root user account in your Mac and restart the computer > Login to Root account and try to access the Creative Cloud App.
Find the steps to enable Root user account : OS X Mountain Lion: Enable and disable the root user
Hope it helps.
Thank you.