I run a lime survey with participants from www.prolific.ac/ . They offer the possibility to include the participant ID of people who come to the survey in the url .

They write: "You can pass the participant ID at the end of the URL as "?PROLIFIC_PID={{%PROLIFIC_PID%}}&SESSION_ID={{%SESSION_ID%}}". We'll replace the {{%PROLIFIC_PID%}} and {{%SESSION_ID%}} with the values of the participants taking part."

I read this and this but couldn't figure it out on my own.

So how can I fill a hidden question at the start of my survey with information from the referrer url? Any tipps?

Thank you!

You should read about the Panel Integration feature, which is exactly for what you are looking for.
manual.limesurvey.org/Panel_integration

Solved. Thank you.