Whats wrong with the formular? (Google Sheets)

I am bloody new to this forum - so if I am doing something wrong, please let me know.

Here is my question: I want to build a URL in Google Sheets where you have to fill out some parts (it for tracking) and then get a URL which is fine for us to track.

Here is the formular:

=WENN(B6="","",VERKETTEN(A6 ,"?utm_source=", B6 ,"&utm_medium=", C6 ,"&utm_term=", E6 ,"&utm_content=", H6 ,"&utm_campaign=", D6 ,"&utm_ad_group=", F6 ,"&utm_creative=", G6))

(I am from germany so "WENN" is "IF" and "VERKETTEN" is "CONCATENATE")

But I always get an error message and cant understand why..

The field A6 is the normal URL like "https://www.x.com" and the other fields are UTM Parameter like this "?utm_source=ActiveCampaign&utm_medium=email&utm_content" and these can be should be filled out individually in the sheet and the you can use the URL.

I hope you can understand what I mean!

Thank you a lot! :)