but while 表示转折,后面能不是完整句子么,直接加名词,我想表达然而不是+名词的意思

ut while 后面不可接名词,
要接完整句子,比如
I have been learning English for many years,but,while I am good in reading comprehension,I still
have difficulty with composition.
I teach at Harvard,but,while a professor,I'm also studying for my Ph.D.in law.
第二句的 while a professor 的完整形式是 while I am a professor ,
I am 被省略了.
另外,but 后面要加逗号
希望帮到了你,
我是加拿大人,我英语老师.