That does seem very long...
Things to check could be ( in the order I'd look):
1. Brake settings on the speed control? (Reglereinstellungen)
2. speed control set properly to the transmitter?
3. Transmitter brake travel limited?
4. Diffs on the car tight?
5. are you running a one-way (Freilauf) on the car and are the tires slipping at the back?
6. Tires on the rims?
More questions PM me and I'll give you the full rundown in German...