Q: in settings when i touch game center app my iphone6S freezes , and when i open game center app i get a blank page and nothing happens , how can i solve this problem ?

Hi, soheilstaar.  

Thank you for visiting Apple Support Communities.  

It sounds like your iPhone will become unresponsive when attempt to access Game Center via Settings.  Since you have reset and restarted the device, let's force all open applications to close.  Once this is done please restart the device once more and then test.  

Force an app to close in iOS

The next step would be to go through the article below due to the blank screen when attempting to access Game Center.  

On your iPhone, iPad, or iPod touch

If you can't connect to the iTunes Store on your iPhone, iPad, or iPod touch:

1. Make sure that your date, time, and time zone are correct. Tap Settings > General > Date & Time. Time Zone might list another city in your time zone.
2. Make sure that your iOS software is up to date. Tap Settings > General > Software Update to check for updates. You can also connect your iOS device to iTunes and click Check for Update on your device's Summary page.
3. Check and verify that you're in range of a Wi-Fi router or base station. If you're using cellular service, make sure that cellular data is turned on from Settings > Cellular. If you're connected to cellular data, larger items might not download. You might need to connect to Wi-Fi to download apps, videos, and podcasts.
4. Make sure that you have an active Internet connection. Check your device's user guide for help with Internet connection.
5. Check to see if other devices, such as portable computers, are able to connect to the Wi-Fi network and access the Internet.
6. Reset your Wi-Fi router by turning it off and then on again.

If there's still an issue, learn what to do if your device won't connect to a Wi-Fi network.

If you can’t connect to the iTunes Store

Cheers