Вот пример письма благодарности на английском для 9 класса. Замени [Surname], [instrument], [Your Name], [City] и [Date] на реальные данные.
Dear Mr. [Surname],
I am writing to thank you for the instrument I bought from you recently. I am very grateful for your kindness, professionalism, and the care you took to ensure that it was in excellent condition.
The [instrument] is of high quality, and I appreciate the tips you shared about tuning, maintenance, and practicing routines. Your advice has already helped me start learning more effectively, and I am motivated to practice regularly to improve.
I also appreciate the fair price you offered and your willingness to answer my questions. I will take good care of the instrument and will reach out if I have any questions about its maintenance or setup in the future.
Thank you again for your generosity and for sharing your time and musical knowledge with me.
Sincerely, [Your Name] [City], [Date]
Если хочешь, могу адаптировать под конкретный инструмент (например, гитара, виолончель и т. п.) и добавить более личную деталь. Сообщи название инструмента и имя певца/продавца.