Wǒ huì jǐnkuài.
我会尽快。
As soon as I can.
Notes:
我(wǒ): I
会(huì): will
尽快(jǐnkuài): as soon as possible
Example:
A: 这个项目什么时候可以完成?
Zhè ɡe xiànɡmù shénme shíhou kéyǐ wánchénɡ?
When will you finish this project?
B: 我会尽快。
Wǒ huì jǐnkuài.
I will finish it as soon as I can.