Исправьте ошибки. ПОМОГИТЕ ПОЖАЛУЙСТА.

1. he has been an actor since he has arrived here
2. i have been to Germany in 2001
3. We have student English since three years
4. They have been learning this course during three weeks

1. he is an actor since he has arrived here2. i was in Germany in 2001 или I have been to Germany        (без даты)3. We have studied (have been studying) - (если учили present perfect continious) English for three years4. They have been learning this course for three weeks