VISA X for studies and internship

Hi,

I have an X and got a residence permit for study purpose in Tianjin.
This resident permit will expire on july 31st.
I found an internship in Chengdu for the next 6 month.
Can I apply for a new residence permit in Chengdu ?
Should I go to Hong Kong to get a new F?
If I go to Hong Kong and get a L, can I still transfer it to a F back to Chengdu ?

Thanks a lot !