On WhatsApp, sending photos or videos via Share or Gallery attachments are obviously downgrading the resolution of our files. But Whatsapp lets us send documents up to 100 Mb. So #Photos and #Videos (which are less than 105 Mb) can be sent without any quality compression IF And Only IF; they are sent as Documents:
Click on the attachment and choose Documents, at the top of the screen (in Android phones) or at the bottom of the screen (in iPhones) you’ll find: “Browse other docs” , click on it and choose your photo or video (should be maximum 105 Mb) and boom! Whatsapp will send the file without affecting its quality and resolution.