Please help us help you and fill where relevant:
Your LimeSurvey version: 6.16.8
Own server or LimeSurvey hosting: yes
==================Dear forum,I am currently trying to find out whether the following setup is possible:We will run a main survey using LimeSurvey. After completing it, the respondent will be redirected to our server, where they will answer additional questions. We have not yet tested which parameters will be passed along, but we hope that this will also include the ID. This is a fixed component.After that, we would like to redirect the respondent to a second survey in LimeSurvey, where further questions need to be answered. However, for this, the original ID would need to be passed along so that we can match the respondents later.Is this possible? Thank you!

Please read the manual.

Prefilling with GET parameters - www.limesurvey.org/manual/URL_fields/en

To pass ID and TOKEN I add this to the redirect link: &X1={SAVEDID}&X2={TOKEN}

X1 and X2 are question names in the second survey.