In your time calculations remember that there are passport controls for going out from Schengen Area, at difference of UK that there is passport control only when arriving. And in DTM there are only like 2-3 booths so it can get congested, and AFAIK there aren't special lines for EU citizens.

Also according to Google Maps it can take up to 35 minutes in workday in car to reach to the airport, I suppose that since it'll be a Sunday you'd have to leave relatively early from the match to don't get stuck with post-match traffic, that can be terribly bad

Another option is to take the 19:12 train from Signal Iduna Park station to Holzwickede (19:26) where you can take a short bus/taxi to the airport, but you'd only watch the first half :( so probably not an option