-Yes, just ask your friend to do it. Read these links for the translation requirement by USCIS:
http://www.nolo.com/legal-encyclopedia/free-books/fiance-marriage-visa-book/chapter4-14.html
http://www.immihelp.com/immigration/document-english-translation.html
https://www.legallanguage.com/legal-articles/uscis-translation/
另外,我的同事用英文写的介绍信,可以吗?
-Yes.
盼回复。
洋芋蛋