英语作文:my biggest challenge is learning Chinese

I am an American and stayed there all the time. But when I am a middle school student, I come to China as an exchange student. In China, I meet many difficulties. The biggest challenge for me is to learn Chinese. Oh, god, it is so hard. There are so many Chinese and every word has many meanings. What's worse, the same pinyin may have various meanings and intonation also makes great difference. I don't know how to open my mouth. Although there are many people help me, I still find it difficult to learn Chinese well.

我是一个美国人并且一直呆了那里。但当我是一个中学生的时候，我作为交换生来到中国。在中国，我遇到了很多困难。对我来说最大的挑战就是学习中文。哦，上帝，太难了。汉字实在太多了，而且每个字又有很多意思。更严重的是，同一个拼音还可以有不同的意思而且音调不一样，差别也很大。我都不知道如何开口了。虽然有很多人帮我，但我还是觉得很难把中文学好。