Hi @UlrikLork,
If you are a teacher who would like to submit a file on behalf of a students, you can follow the How do I submit an assignment on behalf of a stude... - Instructure Community guide to do so. Please note that some schools/institutions do now allow teachers to take this action, so if you do not have the option available, you'd need to discuss that with your local Canvas team (usually in the eLearning / IT / Digital Education areas).
Hope this helps!
-Chris
