For God's sake， stop apologizing. It's perfectly understandable that a Chinese person doesn't speak entirely correct English； there is no need for you to apologize for your English everywhere you go and to whomever you meet. And stop saying that you don't know anything about your specialty.
In fact， you know a good deal， and you certainly know things that Western scholars don't know. Westerners do not consider excessive modesty（谦虚） a great virtue as Chinese people do. We tend to take things at face value. Phrases such as "I'm sorry to have wasted your time" are considered very embarrassing； if， in fact， you believe you are wasting my time， you should stay out of my office， not give a report to the seminar（讨论会）， not give a paper at the conference.
If you are terribly shy and modest about your knowledge and ability in your field， if you do not speak up for yourself when you arrive at an institution as a researcher， for example， you may find yourself working as something like a "lab tech" washing text tubes instead of doing the scientific research you are in fact fully capable of doing.