Thanks for your response!
I think I already tried this approach and it didn‘t have an effect on the outcome, so I assumed that it would change the separation for thousands (atleast that was the topic of the article i found this line of code first).
But I will try it again anyway!
My second attempt was just using the „doc.get_formatted(„grand_total“) function and it did work for the comma, but the problem i got then was that it added an euro symbol infront of the value (€123,45) which is also not possible to use.
Maybe there is a way to get rid of this „€“ symbol instead?