Hi @Andreas Lau,
I'm glad to hear you solve the problem ,if you have any issue about SharePoint, you are welcome to raise a ticket in this forum.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others." and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[Microsoft Graph - Add Worksheet responds with Invalid Request]
Issue Symptom:
Get an "Invalid Request" as a Reponse when trying to add a Worksheet via PHP and Microsoft Graph
Solution:
Check the id and found using the wrong id. Reacquire the correct id fix the issue
You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks for your understanding!