Help with Game Engines

[GoldenPlaya3]

Hello friends, I am a computer engineering student in my second year and I have some questions for you. We are studying the C++ language and I want to improve myself in this language. I want to create mobile games. I heard that Unreal Engine 4 supports the C++ language. What do you think about this game engine? Or should I learn C# and switch to Unity? I have a future plan to sell the games I create. Which one would be better for selling games? Are there any differences? I would appreciate it if knowledgeable friends could comment.