Sorry if I sounded a bit too harsh, but since you asked me via WeChat, I will answer.

First, forget about research internships—now is already too late to apply this summer. 

Then, mind that there are different types of Masters' programs—research-oriented, and course-oriented. The former largely resembles a PhD program: perhaps it's better to work with the professor at the Chinese Academy this summer. A letter from him/her speaks to your research ability, which is exactly the point a research-oriented Masters' applicant is trying to prove. Even if you're applying to a course-oriented Maters', not sure if it helps to work as an admin staff, which is pretty much irrelevant to your excellence in coursework (which matters for such a program.)

Of course, I can only speak about things that I myself have experienced. Therefore, since I have never applied to a Masters' program nor have I been admitted to one, I basically don't know what to tell you.