Why the wifi is unstable?

Hello

I have a tablet Onda v80 se

The wifi is completely unstable since I got it.

To explain you better, when the screen goes in stand by, the wifi disconnects too after a while. When I turn the screen on again I can see that it is reconnecting.

Could you please help me?

I got this tablet to my mother to talk together since we live in 2 different countries, but since there is this problem she doesn't get rhe notifications until she turn on the screen again from the stand by.

Thank you

Giuseppe