Notifications from Whatsapp, Gmail, Telegram, and the like, don't work with this mobile because the layer they put over Android doesn't play well with the apps being in background, because is over zealous with power savings: it just kills processes when it feels like it.

What I have done, just don't ask how neither why, is to dial *#*#46360000#*#* and uncheck “Enable background resource control”. Works superb, at least for now.