I'm not an expert regarding the requirments of a master degree in Accounting. But I just took a look at several study websites, where you can find informations about most of the master programs that exist in Germany.
First of all, it is important to know that the requirments for the same master degree (for example 'Accounting') vary between the different universities that are offering it.
What I have found out about a Master of Accounting (often called also: 'Master of Taxation & Accounting' or 'Master of Finance & Accounting') is that normally you have to proof a certain level of Mathematics from the Bachelor. If you have already succeeded a bachelor degree in Mathematics, you are propably fulfilling this requirment.
At the same time there other requirments as well. For Accounting you also need a certain level of business or economic courses from the Bachelor. If you are missing those, you can possibly repeat them.
Sometimes you even have to provide evidence that you already have some working experience in this field.
But as I said it really depends on the university, so you should take a look on the websites of the universities. There you can look for 'Master of Acounting' and find all the informations.
Maybe the following page is a good starting point, but unfortunately only in German. It shows the universities that are offering 'Accounting' as a master program.
I hope, I could help you.
If you have more questions, feel free to ask them :)