Translation of "ability" into Chinese

Developing his ability of speaking English, it seems, is his purpose of studying abroad.

看来他出国学习的目的是要提高他说英语的能力。

I don't know how long I'll have to wait before my creative ability improves.

不知道要等多长时间,我的创作能力才能进步。

Children's resilience, capacities and ability to contribute to peacemaking and peacebuilding should not be underestimated

儿童的复原力、智能和促成和平及建设和平的推动能力都不容低估。