OK. Literal interpretation.
You can truthfully answer no even if you do not intend to pay the fine. You have not been convicted.
But... if you don't pay the fine and you are ever asked again, such as upon entry, you might have to answer yes.
So yeah, answer quickly and pay the fine.
Depends on the fine print.
German law has something called a Strafbefehl, a non-negotiable, court-approved offer of a plea bargain. One can take it or request a full court case. The Strafbefehl is only possible for a misdemeanor, and differences between a crime and a misdemeanor are problematic when it comes to translations.
It could also be a simple fine ...
Fact 1: You haven’t been convicted. Fact 2: You have been fined. Fact 3: You have committed an offence (that’s what you told us). Fact 4: There is no record in Germany that you were even accused of an offence. Fact 5: You have never been charged of an offence.
You should answer the exact questions that you were asked truthfully. The truthful answer to ...