The best would be a complete interaction between the two platforms (with shared logins and gradings), but since my internship is almost ending I will not have the time for that anymore.
I now just managed to make a block where I display the information I want (Hurray!), but I will definitely take a look at your suggestions for Local_plugins and the Database_activity!
Thank you very much :D
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Ps: Do you have suggestions for the quiz-part where a user can choose from a dropdownlist which is filled with external database content?