WhatsApp for Realme C67

Poor video call quality usually comes from a weak or fluctuating connection or WhatsApp's data-saving limit, so first test on a stable Wi-Fi network and in WhatsApp open Settings > Storage and data and turn off 'Use less data for calls.' On the Realme C67, also go to Settings > Apps > App management > WhatsApp > Data usage and allow both mobile and Wi-Fi background data, since ColorOS data-saver restrictions can throttle the live video stream. Updating WhatsApp from the Play Store also helps, as older builds had call-quality bugs. See how others solved this on Reddit

Lag is often caused by a bloated cache and a large media library. Clear the cache via Settings > Apps > App management > WhatsApp > Storage usage > Clear cache (this does not delete your chats), then inside WhatsApp open Settings > Storage and data > Manage storage to delete large forwarded videos and files. Keeping the app updated from the Play Store and restarting the phone occasionally also smooths out the slowdowns. See how others solved this on Reddit

ColorOS aggressively limits background apps to save battery, which is the main cause of late WhatsApp alerts. Go to Settings > Apps > App management > WhatsApp > Battery usage (or Power consumption) and choose 'Allow background activity' / 'Don't optimize,' then open the recent-apps screen, swipe down on the WhatsApp card and tap the lock icon so it can't be cleared. Also confirm notifications are on under Settings > Notification & status bar > Manage notifications > WhatsApp. See how others solved this on Reddit

The screen blacking out during calls is the proximity sensor thinking the phone is near your ear. Clean the top of the screen and remove any thick screen protector covering the sensor area, then dial *#899# (engineering mode) or use Settings > Additional settings to run a proximity sensor test. If it still misfires, restart the phone, and make sure WhatsApp has its permissions intact under Settings > Apps > App management > WhatsApp > Permissions. See how others solved this on Reddit

When the mic works elsewhere but fails on calls, WhatsApp's microphone permission has usually been restricted. Go to Settings > Apps > App management > WhatsApp > Permissions > Microphone and set it to 'Allow,' then check Settings > Privacy > Permission manager > Microphone to confirm WhatsApp isn't blocked there. If it persists, clear the app cache and make sure no call-recording or noise-cancellation app is holding the mic input. See how others solved this on Reddit