We made some changes on the servers yesterday morning and now, after 24 hrs we think that the issue is solved.
The highscore list, as first thought, was not the only reason for the difficulties. Another problem came from matchmaking and it caused a crash if very many players wanted to run a race.
Hint: If you wish to switch the game language, right-click on the game in your Steam-library, select “Properties” and choose your preferred language.
We wish you lots of fun on the racetrack!
Your Quantum Rush team