i have updated my nokia lumia 625 to windows 8.1 . Recently (few weeks before),my phone memory takes about 6.27gb of space.i cant update my xbox music and all other inbuilt apps. please help me.
I think you are hitting the upgrade bug that Microsoft and Nokia acknowledged.
There is not a simple workaround right now but you can try to follow the instructions provided there:
"So Microsoft is allegedly doing something at some time to address this bug. But give Nokia some credit for not waiting on the firm to do the right thing: It’s starting to ship a new app called Storage Check with new low-end Lumia handsets, like the Lumia 620, that addresses this problem now. (I have a Lumia 620 but didn’t get this app, presumably because I purchased it early on.)
The Storage Check app includes a Clear button that clear out much of the storage space used by the Other category. This category will still fill up your free storage space over time, of course, but at least the app provides a way to manually fix things."
You can rather download the 'UpdateAdvisor' app from the Windows Store and use it to clean the temporary files and the others category. It actually helps you to free up some space for your next Update.