Is there a foot surgery for flatfoot / overpronation?

Yes: There are several procedures or combinations of procedures to help cure flatfoot. You would need an evaluation to tell exactly what is needed.

Flatfeet: There is. But to determine how extensive the procedure is. Your feet will need to be evaluated by a surgeon. You'll need x-rays and a gait analysis to determine what procedures will correct your deformity.

Surgery : Yes - but you need to approach this with your eyes wide open . First get an evaluation and x rays and ask lots of questions. Be honest with your expectations when you speak to your surgeon.

Yes : depending on the flexibility of the foot and the strength of the tendons of the foot different surgical options are available. Some are simple, and some require fusion of bones and/or transfer/lengthening of tendons. A foot and ankle specialist can discuss what is bets for you.