Thanks @joffm, @tammo and @tpartner for your answers and your solutions. 

Indeed, userid would not work, since clickworkers only works with the parameter user_id. 
What I have tried in the meanwhile and what for any reason worked was:

1. I copied my survey, 
2. I deleted my ID question and created a new one
3. and (most important) I disabled the Recaptcha from my survey.

For any reason the passthrough does not work when I use a Recaptcha. I will try it with my original survey an the life setting tomorrow and keep you posted if this is a helpful solution. Otherwise, I will go with tpartners solution (finger crossed). 

Thanks and best regards

Lotta

Usually these things don't work if the question with the attribute is not on the first page of your survey (captcha, welcome text, etc.). Basically the URL changes after the first page has opened and then the ID is gone.

What I showed successfully was with the captcha and the welcome screen.
video follows.
Tested in Chrome, Firefox and Edge.

@tammo: No with spaces, as you see in the "Haus vom Nikolaus" example.

But as I said: I tested in 2.73.1. and she uses 2.62.2.

Anyway, you have some alternatives to try.

Joffm
 

Yes, it workes for me with the welcome page but not with a captcha. However, to be sure I disabled the welcome page and it works in the life session with clickworker but for any reason I have cases with and cases without an ID passed through. I assume this is sth. I have to discuss with clickwork. 
I might also a bug in my first questionnaire version which dissolved when copying the survey. 

Thanks all for your help, solutions and time