Proofreading?

Hi Teachers, please help correct my article if there are any grammatical mistakes. many thanks.
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Dear John,

How’s everything with you?

Sarah invited me to attend her graduation ceremony next Sunday; I have been thinking what I am going to dress up that day. My sister advised me to try shopping online and she offered me some helpful suggestions. I bought a blue dress in an online store, which specializes in clothes, shoes and jewel for girls aged between 15 and 20. Personally speaking, I find online stores are very convenient, because I don’t need to walk along the streets but can get what I want just operating a computer. What if I feel uncomfortable wearing the dress I bought online, the owners of the online store said I can change it for a new one anytime. So I recommend you to go shopping in this online store if you need to buy clothes.

Give my best to your family.

Yours sincerely,
Mary