Conversation so far:
What is the Borussia Mönchengladbach?
Borussia Mönchengladbach is a professional football club that plays in the Bundesliga, the top flight of German football
Where was the team Borussia Mönchengladbach located?
The Borussia Mönchengladbach professional football club is based in Mönchengladbach, North Rhine-Westphalia, Germany.

Question: How long was he on the team for?
Self-contained rewrite: How long was Allan Simonsen on the Borussia Mönchengladbach team for?