Geartronic spins- How to repair?

The search function is unfortunately still out of order, therefore my new thread. My Geartronic recently spins. Either it doesn’t turn at all, or switches like crazy into gears, where it has nothing to look for. I suspect that the electronic control on the gearbox, or the Mechatronic has suffered damage due to the extreme heat effect of the engine (T6). The heat problem has been solved by now, but now the gear has to be repaired. The Geartronic seems to be a GM (Opel) gear (Made in USA). Maybe someone knows who can repair this type of gear in North Rhine-Westphalia cost-effectively?