Nín xiān qǐnɡ.
您先请。
After you.
Notes:
您(nín): you(repectful form)
先(xiān): first
请(qǐnɡ): please
Example:
A:您先请。
Nín xiān qǐnɡ.
After you.
B:谢谢。
Xièxie.
Thank you.