我今年秋天要到中国去留学，高兴极了

外国朋友们好：(Hello, friends!)

我终于决定安排了今年的计划。（I have finally decided on my plan for this year).
很多考虑以三思后，我斩钉截铁地决断了决定今年秋天要到中国去留学。（这样说不好。考虑很多就不能说“斩钉截铁”了。）（After thinking about it a lot, I am resolute in my decision to go to China this fall to study abroad).
我一直对去中国留学一直很感兴趣，可不知道最合适的时间应该去什么时间最适合去。（I've always been immensely interested in studying abroad in China, but I didn't know when the best time to go was).
决断做了最后的决定了以后，我很高兴起来了。秋天，我等不了了。After making my final decision, I became very happy. I can't wait for this fall.
虽然我当前的中文老师很棒，但貌似因为她不是中国人，所以貌似不能很清楚地回答我的复杂的问题回答得很清楚。连中文单词细微的区别（比如说，近同义词之间）连她也不清楚。(Even though my current Chinese teacher is awesome, because she is not Chinese, it seems she can't answer my complicated questions very clearly. Even she does not understand the tiny differences between individual words very clearly (between near Chinese synonyms, for example).
我的确希望越学越会好！I do hope that the more I study, the more I will be competent.

顺便说一下，我刚才刚刚学的最喜欢的成语就是“狼吞虎咽”，因为我觉得我这样总是像是在吃中餐。＝） （“刚才” makes me feel that you learnt that Chengyu right before you wrote this composition.）

By the way, my favorite chengyu that I've just learned is 狼吞虎咽 because I feel like I always eat Chinese food like this.