Dear [Friend's Name] and your wonderful family,
I am writing to thank you sincerely for the amazing three weeks I spent at your home. Your warm hospitality and kindness made my stay unforgettable. I truly appreciate the comfortable room you provided and the delicious meals you prepared every day. It was a pleasure to experience your culture firsthand and feel like a part of your family. Thanks to your support and conversations, my English skills have improved significantly. I now feel more confident speaking and understanding the language. I am very grateful for this valuable experience and hope to see you all again soon.
Best regards,
[Your Name]