What is your question ?
Are you looking for the English equivalent of the teacher's remarks ?
Do you have a textbook or dictionary where you could look it up ?
Your teacher said: "Hello, students. I am your teacher !"
There is no reason for you to flunk. Get busy and make up your mind that
you're going to do all the homework and reading.
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I think there may have been a slight oh-oh in there:
You said that your teacher is a 'she', but the German word "Lehrer" means a
male teacher. She might have actually intended to say "Ich bin dein Lehrerin !"