Backup everything to the cloud first on your old Lumia 520. Go into settings and check the box for photos, contacts, SMS etc.
Do not reset it.
Sign in on the Lumia 925 and select restore from your previous Lumia 520 as the option with the correct date/time stamp. Sit back relax and enjoy the transfer.
You can then arrange the tiles on the 925 in the same order as the 520 - it will not auto do it for you. Also back up WhatsApp first on the 520 before you sign in on the 925 to get all your messages back in one piece. Good luck.