во Какой ответ? Had been buying Had been bought Had bought

Dear John,
Sorry for not answering, I was really busy with my homework. Thank you for your letter, I was really happy to hear from you again.
Well, as you know, i went to London with my parents last week. Our journey was absolutelly breathtaking! We lived in the hotel near Big Ben. We went to a guided tour. It was really exciting to meet historical places of the city. Moreover, we went sightseeing. We also visited different squers, parks and museums and met with local culture.
Sorry, I have to go now. My dad is calling me.
Keep in touch!
Yours,

Paul and Oliver often have picnics in the picnic area in summer.
Paul and Oliver usually play sports at the sports center on holiday.
Paul sometimes watches birds in the Wales parks in August.
Paul and Oliver always have countryside walks in the Wales parks at weekends.
Oliver often rides a bike in the Wales parks in summer.
Paul sometimes rides a horse  in the Wales parks on holiday.
Paul and Oliver usually fish in the Wales parks every summer.
Oliver often climbs mountains in the Wales parks in summer.
Paul and Oliver sometimes buy souvenirs in the Wales parks on holiday.