Yes, OPPO A37 has Corning Gorilla Glass 4 Protection which is one of the best scratch resistant technology.
No. Oppo A37 is not a waterproof mobile.
Yes, You can download new ringtones in OPPO A37f. Once you save the music or the tone, which you want to set as ringtone, please follow below mentioned steps
Go to Settings > Go to Sound > Click on Ringtone > Select the ringtone which you want to set
The phone runs on 1.2 GHz Qualcomm Snapdragon 410 Quad Core processor.
Once again Oppo has presented us with a device that is functional, to the point and performs just as expected.