@amca Remember, my major was electrical engineering!
A field effect transistor works very simply, by using an electrical field to open or close a path. There is nothing hard to understand about that.
A bipolar junction transistor (which is a less common sort nowadays), I forget exactly what is going on in that. But it is similar.
What the ‘quantum’ stuff involves is that there are a lot of EMPIRICAL LAWS that are called ‘quantum’. They are like Boyle’s Law before invention of the Ideal Gas.