You can only reset your passcode WITHOUT losing all data by having a backup on iCloud or you computer. If you do not have any backups then you have nothing to restore from and you will lose all data after the passcode has been reset.
You can reset your passcode by following the instructions in this article by Apple ➔ How to reset your passcode on a disabled iPhone. You will need a computer for this task and all your data on your iPhone will be wiped clean in the process.
If you have a backup created then you can ➔ Restore Your iPhone from that backup file. If you do not have a backup file created then you will lose all your data on the iPhone.
If Photos, Messages and Contacts are synced to iCloud then you will be able to retrieve them after setting up iCloud on your iPhone after you reset the passcode and sign into iCloud.
Axel F.