Add spaces: Jacobi'searlyeducationwasgivenbyanuncleonhismother'sside,andthen,justbeforehistwelfthbirthday,JacobienteredtheGymnasiuminPotsdam.
Jacobi's early education was given by an uncle on his mother's side, and then, just before his twelfth birthday, Jacobi entered the Gymnasium in Potsdam.