глагол to be быть, находиться употребляется в Present Simple, Future Simple, Past Simple. Есть короткая, вопросительная и отрицательная формы. I'm a girl. I am not a girl. He's a boy. He is not a boy. Are you a girl? Is she a student? Yes, she is. No, she isn't. Прошедшая форма was or were. I was a student ten years ago. Was she a student ten years ago? Yes, she was. No, she was not. Were you students fifteen years ago? Yes, we were. Будущая форма Will you a teacher next year? Yes, I will be. No, I won't.