C# + C++ = Beef:
https://www.beeflang.org/docs/foreward/
C++ almost definitely has better performance in most cases but if you're not making a Triple-A game with lifelike graphics and sophisticated AI then the difference probably doesn't matter (except maybe if you target some very low-end devices).
I'd say just pick whichever you like best. And maybe also look into what kind of libraries the languages have for game development purposes (graphics, sound, etc).