Does the submission happen automatically at the end of the exam period or do I have to click on a button ("Submit" or similar)?
As a rule, a submission button must be clicked in the test module (multiple choice, etc.). There is a clear feedback that the submission of files or the answering of test questions has been completed.
In the Assignment Module (e.g. uploading a file at the end of the examination period), the submission is also controlled by buttons.
Be sure to take the opportunity to participate in mock exam offerings to go through the exact process.