Present perfect VS Past perfect

__________ the teacher __________ (come) back yet? I would like to ask her a question.

The twins ___________________ (play) the piano for six years.

I ________ (have) three lessons today and I still have two more later this afternoon.

Remember that after you __________ (sign) the contract you won't be able to change your mind.

The boy told me that he __________ (lose) his train ticket and didn't know how he would get home.

By the age of 45, Mr. Johnson __________ (establish) himself as a NGO leader.

My dad __________ just __________ (move) to his new office.

At the conference, scientists reported that they __________ (find) a cure for the rare disease.

We __________ (clean) our flat all day long.

Fresh fruits and vegetables are very difficult for consumers to get, and they are expensive these days because a typhoon __________ (sweep) across the island.