I worked the last time on my project in december. Today I launched Intel XDK again and installed a update. After this my Project was gone.
Is there a backup of the last stands of my projects or are there other ways to restore them (for example via an .apk)?
Have you check the folder that your project existed in?
There is no code in the XDK that removes a project from disk.
If its there, you should be able to simply import it as an existing app.
If it is not there, send me a private message and I can see if I can find something on our end.