how can i change the language of iphone 5 i have try Above formula but it was not change.

To change the laguage of your iPhone go to Settings > General > International. The option to change the language is here.

I have an iPhone provided by my Hong Kong employer and I've changed all the language settings to English but when I go into ap store its still in Chinese? Any help would be appreciated.

You'll need to change the country of the App Store. On the home page of the store, scroll to the bottom and tap on the flag I think.