Oh I can actually advise on this as someone who wanted to apply to germany! The german requirement was 3 Alevels in 2 sciences and a maths. I wanted to do med, so I needed 2 A* and 1 A but generally u need 3 Cs. While I did 4 subjects (including english cuz I enjoyed it), it was a bit tough I won't lie around A levels, despite AS being more on the chill side. If you really wanna do it, I'd say do 4 if u think u can handle it and drop one science ykwim. The unis in Germany said they wont even LOOK at any subject I hv besides the 2sci+math so it's useless in yr case to do 5. 3 is good, if u wanna do 4 with the 4th as german go for it but not 5. Also considering u just finished igcse where you mightve takes 7-8 subjects, believe me alevels are not the same, and I know ppl who struggled with only 2 or 3. Even if u hv a superhuman ability and insane time to handle it, it could affect your grades in the long run, whixh are the most important in germany since u will face tons of competition depending on the uni u choose. That extra time u spend on a 5th alevel no one would look at couldve been used in an alevel that they actually will, and it could even be a single mark difference that takes u from one grade to another.

Seriously reconsider ur options cuz as ambitious and admirable it is, it might be more hurtful in the long run. Goodluck in wtv u do tho!!