Language support in the Openstack Dashboard (horizon)

Issue

• We've installed the openstack dashboard (horizon). I noticed that a user can change the language of the interface under settings. Currently a handful of languages are available.
  However a few big ones, like German or Italian are missing, whereas for example Dutch is offered.

• I have therefore two questions:
  1) Are there more languages that can be added?
  2) If it is not possible to add German and Italian, is it possible to remove everything, but English?