Hi. I am leaving Hong Kong in April. I think I won’t be back for at least half a year. I think the situation in Hong Kong won’t get better soon. So I decided to visit my friends in Australia, Europe and Canada. Thank you for giving me the chance to teach Tom and I enjoy every moment with him. I would not use "and" here. these seem like separate things, so either join them, or separate them; Also consider past tense (but that is optional)? Thank you for giving me the chance to teach Tom. I have enjoyed every moment with him. Thank you for giving me the chance to teach Tom; I enjoy every moment with him. If you need anything I can help with, please feel free to ask. any thing --> anything .. I can help with. Like questions about piano or need accompaniment for Tom’s competition. Not a sentence. If you need anything I can help with, such as questions about piano or should you need accompaniment for Tom’s competition. please feel free to ask. I will do as much as I can to help. Since I will be leaving for a while, I think it’s better to refund the tuition fee to you. Technically refund is return, so "to you" is redundant, but could leave it if you feel strongly about it.