l can speak some English

Dear Tom，
I am Wu Xie. Yesterday, we have make an outh (?) ceremony for our 18th birthday. I am very happy because my teacher sent some postcard for me. After the students had prepared a program, it was a lot of fun. Finally, I went to express my thanks to my parents and teachers. They often offer me suggestions when I have trouble or questions. Also, I think friends are important in my life. l can study with my friends.

<em>可能这是不是oath ceremony?</em>

<em> 您是18年de生日吗？生日快乐！</em>

l can speak a little English

Dear Tom，
I am Wu Xie. Yesterday,we has make had an oath ceremony for us our 18th birthday. I am was very happy because my teacher sent some me a postcard for . After, the students prepared a program. It was very fun. Finally, I want to express thankgivling my gratitude for my parents and teachers. They were often offer suggestions when I have trouble or questions. Also, I think friends was are important in my life.l can study with my friends.

often offer suggestions sounds a little awkward ("off...off" sound)

you could say: "they often help me"