I’m sorry to hear that you’ve accidentally deleted Cubasis from your iPad.
With the release of version 1.9.8 posted Feb 16, 2016 Cubasis supports iCloud Drive to store and access project files and data. Please refer to the following Apple link to learn what the feature is capable of:
It depends on the type of backup strategy how to restore Cubasis on your iPad.
If you have stored your Cubasis project files to iCloud Drive, you can re-install Cubasis from the App Store and import your files via the iCloud Drive afterwards.
In case, you did not backup your projects it is strongly suggested to get familiar with the available options how to do so, to prevent yourself from loosing important files. Please have a look at the “MediaBay” chapter in the in-app help of Cubasis, to learn more about the options about how to backup projects/files.