Revert package manager upgrade (Debian)

Hi,
so i upgraded owncloud from 8.2.2 to 9.1 using the deb http://download.owncloud.org/download/repositories/stable/Debian_8.0/ / release channel.
Unfortunately I forgot that I should have done this in steps. Now I reverted the update manually and upgraded to 8.2.7 manually.

Now apt-get still thinking I am running 9.1. How can I revert this? And is apt-get remove owncloud also removing the data and config folder?
Thanks a lot!

Have a look at the manual of apt-get, especially how to downgrade packages. Normally it should be possible (after you have choosen the correct repository for oC 9.0) to "downgrade" the package to oC 9.0.4. Afterwards you can do the next step to update the package to 9.1.0.

But as oC 9.1.0 showed a few bugs you could also stay with oC 9.0.4 and wait for the release of 9.1.1 which is recommended anyway for productive systems.