I’ve not had to call support recently, but there used to be an English option. If not, select the German option and just ask, clearly, for someone who can speak English once they answer.
If you’ve already tried resetting your Horizon box back to factory defaults, then Error 2010 sounds like a cabling problem.
If checking all your own cabling doesn’t solve the issue, including that thing that converts a 2 or 3-hole socket into the right connectors, then I guess UPC will send an engineer out to start checking things.
https://support-en.upc.ch/app/answers/detail/a_id/9646/~/horizon-hd-recorder%3A-error-message-1090-or-2010