Help me correct this, please

I'm sorry for not writing to you earlier but I'm studying hard for an English exam.
I'm writing to thank you because you let me stay with you and your family last Christmas.
It was such a wonderful day that it's hard for me now to go back to my usual routine.
I know that a week is not enough time to discover the whole of London.
The sightseeing tour was fantastic and I really love "Mamma Mia", the musical.
I remember that we spent long hours having a cup of tea with your grandmother while she told us old stories.
I'm sure my English is better now to thanks her.
For the last 2 months I've made a lot of progress.
I think I will be able to move to the new house next week.
I'm really looking forward to showing it to you.
That's all now . Write soon to tell me all your news.
Give my love to your family.
Best wishes,

It is best to either use all contractions (e.g. I'm, it's, that's) in the text or write it all in full (e.g. I am, it is, that is) as a mixture of the two sounds 'wrong'. 

Remember to use a full stop at the end of each sentence.