Like others have said, make sure your parents are 100% behind your decision. If there's any doubt at all then the school can easily say no, just because your parents don't agree with your decision.
One of my mates dropped Graphics at the end of Year 10 to study extra Maths as he was doing pretty poor. I'll try my best to advise you based on what he did.
Once your parents are behind you, talk to your Business teacher first to tell them what your doing (if you can't trust them/don't like them/don't think they are very understanding then I would skip this step), then go to either the Head Teacher or person who sorts out the timetables. Discuss it with them, and make sure they understand. It's likely that they wont allow you to do it to begin with (unless they are extremely understanding), so if you manage to slip in the fact that your parents want you to do it too, then they might back down. You could also mention all of the extra stuff you are doing outside of school to show that you are committed - however this could backfire and the teacher you are speaking to might reply with "Well, why do you need the extra time in school then?"
After that, depending on how it goes, you may be removed from the Business course and allowed to study elsewhere in your own time, or, you might have to have a meeting with a teacher and your parents, but like I said, if your parents support your choice and they're willing to fight for you, then you should be alright.
At the end of the day it's the school's choice, so don't be distraught if they don't let you. You sound like you'll be fine anyway.
My friend managed to drop Graphics, but rather than getting to go elsewhere, he had to carry on going to Graphics to register there, and he just brought in Maths work, so he was still with his Graphics mates. I'm not sure if that was his choice or just a compromise, but it seems likely that's what will happen to you (if all goes to plan) as you'll need to register somewhere.
Above all, have fun and good luck, German is a great GCSE to have and it's extremely fun. I got a B in it this year (could have been an A/A* but my coursework was shoddy
) and I'm taking it for A level.