4. Now, when we that at this time two days ago we (watch) a film at home, it is difficult to imagine (ski) in the mountains.

Ответ:

Now, when we are watching a film at home, it is difficult to imagine

that at this time two days ago we were skiing in the mountains.

Убедись, что используешь правильные формы глаголов watch и ski в Present Continuous и Past Continuous.

Past Continuous описывает действие, которое происходило в определенное время в прошлом. Present Continuous описывает действие, происходящее сейчас.