The first one is correct. Maybe it will look easier with a subject not modified by any adjective: "How should I be?" I should be gentle. "How should a good teacher be?" A good teacher should be patient. I am not going to say more about how a teacher should be; I said that for the purpose of the example. Hope that helps!

The first sentence, "How should a good teacher be?", is the correct sentence. The second sentence is not correct.

2 , that is the asking way u could speak.