Посмотрите правила: 1.GR10-неправильные глаголы. 2.GR5 Модуль 6 образование Present Perfect, 3.GR7 (модальные глаголы-don't have to / have to), 4.GR7 Present Perfect Continuous I-have been working, haven't been working You- have been working, haven't been working He- has been working, hasn't been working She- has been working, hasn't been working It- has been working, hasn't been working We- have been working, haven't been working You- have been working, haven't been working They- have been working, haven't been working