Are there any additional credits or co-curricular activities I can do to increase my credit points for eligibility in Germany for a Bachelor's/Master's?

No, unfortunately co-curricular activities will not help you here, since German university admissions are heavily academic and formula driven. Your eligibility depends strictly on measurable criteria like grades, subject breakdown, and ECTS credit hours completed. Knowing this now will save you time chasing extracurricular boosts that will not count toward your application.

Legitimate Ways To Bridge An Eligibility Gap

Why Extracurriculars Cannot Substitute For Credits

Your German university application is evaluated against your previous grades converted to the German scale, your subject breakdown, and your exact ECTS credit hours, none of which extracurricular certificates or uncredited online courses can influence. In rare cases, a small number of universities accept professional work experience if explicitly allowed under a program's Prufungsordnung, but this rarely awards you actual ECTS credit.

My Advice

Check your credentials against the ANABIN database first to see exactly what you are missing, then read the Prufungsordnung for your target program to see if conditional admission is possible. Focus your energy on a Studienkolleg, bridging semester, or pre-Master's program rather than co-curricular activities, since only these actually count toward your eligibility.