改正如下（改正部分用括号标出）：
A few months after returning (to) the US from Germany,I took part in a college course (on/about) French.Since I have learned to (speak) German well in Germany,I thought it might be (interesting) to begin studying another languague.At the first class,the teacher asked us to do a pronunciation exercise in (which) he would say a word or two in French,and each student would do (his) best to copy.When he got to me,he kept having me (去掉to) say more words,and I finally asked him why."I find it great fun," (he) explained it."In (the) 25 years of teaching at school,it's the first time I've heard an American speak French with a German accent."