Dear granny,
I really miss you. I'm good and how are you? I would be very happy to know, that you are okay too. We have made maintenence and now our house is clean and cosy! I'm studying well. I really love English lessons, but I don't always get 5s. Also I go swimming.My parents and my brother are alright too. We love you so much!And we miss you! We are glad to have such a grandmother!
(для хорошей структуры добавлю окончание)
I'm sorry - I must go now.Because my mom wants me to help her.
Write back soon!
With love,
your name