The internship report should prepare you as well as possible for your bachelor thesis which will be a Bachelor of Science. Therefore, report on your internship project as a whole, a subtask or a specific interesting aspect of it and follow the rules of scientific writing!
Consider the report as a small bachelor thesis with the typical structure: abstract, introduction/problem statement, basics, problem analysis, etc., critical reflection of the chosen methods and the results, conclusion and outlook (or a similar structure). Please consult your course material on scientific writing. Please find my (R. Becker's) comments under Short Guidelines on Scientific Writing.
Use scientifically neutral writing (no “I”, no “we”, etc., even in the introduction). Citation style as described at the Academic Writing Manual on Moodle.
Length: 15-20 pages (including cover page, figures, references, etc.).
You then simply upload both the internship report and the certificate (from the company/organization that you worked there full-time from XXX to YYY, i.e. 35-40 hours per week) to Sharepoint.