Sum per Field fom another table

Good evening,

I have a small beginner problem I can't solve on my own:

I want to SUM the values in my table DIV_2023 in another table, but by value:

The idea is If the value in table Div_2023.Monat is 'Januar' sum Div_2023.Dividende and write it into table SUMMEN - row SUMME where Monat=Januar

then the same with Februar, März and so on, so for each month.

Anybody an idea?

Thanks in advance