Hi Moegagner,
You can select another ringtone via accounts -->Select your account --> Ringtone --> select your ringtone.
The defaultringtone is the ringtone you selected to be your default on Android, other ringtones you uploaded to the phone its ringtone folder might be visibile in there as well as a few other default ones
Storage folder of ringtones ( might be different on your device ) = ( /storage/sdcard0/Ringtones )
Best Regards,
Paul