Привет! Давай подправим эти предложения вместе, используя конструкцию 'have something done'. Вот как это будет выглядеть:
They're painting the kitchen on Saturday.
- We are having the kitchen painted on Saturday.
They're going to service my sister's car next week.
- My sister is having her car serviced next week.
Her parents pay her mobile phone bills.
- She is having her mobile phone bills paid by her parents.
Last summer they built a swimming pool in my friend's garden.
- My friend had a swimming pool built in his garden last summer.
They fixed our computer last week.
- We had our computer fixed last week.
They've reinstalled the operating system on his computer.
- He has had the operating system reinstalled on his computer.
Всё просто, верно? Эта структура помогает показать, что действие выполнил не субъект, а было выполняено кем-то другим для субъекта. Если в предложении указан исполнитель, мы добавляем его после конструкции с 'by'. Удачи с заданиями!