Es ist sehr wichtig, dass Deutschsprache du kennst.
It is very important, that you know the German Language while in German part of Switzerland.
If you want to be "successful" and well accepted in the German part of any Financial jobs, you have to speak, write and converse socially in German. Better still, Swiss-German. Even if it is a low level german skills.
i made do without DE for 6 years? Then I started (restarted) my DE lessons, and I try to speak during meetings, lunches, etc. It makes a big difference.
Du musst sprechen Deutsch!
(ok ok my DE is not that richtig!)