Changing comma to dot with Excel on a Mac

As you can see in the image above, I even have two different decimal separators, one for number in general, and one for currency (euros are supposed to use comma, and I prefer period, as I am used to writing in English and that is also used in programming).

Maybe a question for the Microsoft Product Help Communities.

You don't have to change the whole language for your OS.

You can change language for Excel only, by clicking on Apps in System Preferences->Language & Region.

Also, you can just change the decimal comma to point or viceversa, without changing the language.

Click Advanced:

See if this helps.

https://www.avantixlearning.ca/microsoft-excel/how-to-change-commas-to-decimal-points-and-vice-versa-in-excel/#:~:text=1%20Select%20the%20range%20of%20cells%20in%20which,symbols%20or%20characters%20in%20the%20selected%20range.%20

I think this will show you how to do it, https://www.howtogeek.com/240316/how-to-change-the-currency-symbol-for-certain-cells-in-excel/

Also, a great resource for these types of questions is "Mr. Excel" which has bailed me out many, many times over the past 1-15 years, https://www.mrexcel.com

Good luck.