stop making sense

Preliminary Questions for the Philosopher on the Foundations.
Because I can't wrap my head around mathematical concepts, and hence most of the analytic-philosophical tradition.
Why does Frege think he can reduce arithmetic to analytic logical truths, but not geometry?
What is the fundamental difference between arithmetic and geometry?
In terms of commutativity?
In terms of space and time?
How is synthetic a priori a possibility for geometry and yet not arithmetic for Frege?