Yes, Oppo F9 is a dual VoLTE mobile phone. You can use 2 4G network sim cards at the same time.
No. Oppo F9 is not a water-resistant mobile phone. Be careful !!
Oppo F9 has ARM-Mali G72 MP3 GPU. The peak frequency of the GPU is 800 MHz.
The most striking feature of the Oppo F9 is the big display with the waterdrop notch. It is well designed, delivers good battery life, and offers decent performance for the price.