Conversation so far:
What University did Gottlob Frege attend?
Gottlob Frege matriculated at the University of Jena in the spring of 1869
What did Gottlob Frege study at the University of Jena?
In the four semesters of his studies Gottlob Frege attended approximately twenty courses of lectures, most of them on mathematics and physics.
Did Gottlob Frege then transfer to Gottingen after the University of Jena?
Starting in 1871, Frege continued his studies in Göttingen.
What did Gottlob Frege study at Gottingen?
Gottlob Frege continued his studies in Göttingen, the leading university in mathematics in German-speaking territories, where he attended lectures of Rudolf Friedrich Alfred Clebsch, and Ernst Christian Julius Schering.
Did Gottlob Frege graduate with a degree?
In 1873, Frege attained his doctorate under Ernst Christian Julius Schering, with a dissertation under the title of Ueber eine geometrische Darstellung der imaginären Gebilde in der Ebene.

Question: What did he do after he graduated?
Self-contained rewrite: What did Gottlob Frege do after he graduated?