Since you appear to be on the +2 math track, what is the possible gain from accelerating even more to get on the +3 math track? Also, why would you worry about not doing well in math?
In terms of German and Spanish, would taking them both displace other typical high school academic courses from your schedule? If you have to choose one, German may be more useful if you will go on to PhD study in math, but Spanish will be more useful if you become a physician practicing in the US.
Also, if you do end up being a pre-med (as your username suggests), college courses taken while in high school and their grades will need to be reported on your medical school application. For pre-meds, A should be considered the only acceptable grade.