On each court there are three matches played (2 singles, doubles). Sometimes a country already won at 6pm, sometimes it takes much more time. Hard to predict.
To get from Hauptbahnhof to the Rochusclub normally the best is if you go by public transportation (tram lines).
You understand German? Lots of Dutch do. So look at the bottom of this link and it's pretty well explained. I did it myself three years ago when I was there the last time and it was much faster than 40 minutes as they write on the homepage. I would guess about 20 or 25.
Also look here for the map:
Yes, trainingscourts are on the facility.