WhatsApp for Samsung Galaxy S5 Sport

The Galaxy S5 Sport shipped with Android 4.4/5.0, and current WhatsApp builds require a newer Android version, so the Play Store may block the install or only offer an outdated build. First take every available update under Settings > About device > Software update. If your Android version is still too old, you can sideload the last compatible WhatsApp APK from whatsapp.com/android while it can still register, but this only buys time. Long term the only real fix is moving the account to a newer phone, since WhatsApp regularly drops support for old Android releases. See how others solved this on Reddit

On older Samsung Androids, WhatsApp calls often fail to ring or display because battery and background-data restrictions are putting the app to sleep. Go to Settings > Applications > Application manager > WhatsApp and confirm Notifications are enabled and the microphone permission is granted. Then exclude WhatsApp from any battery saver or 'Smart manager' sleep/optimization setting under Settings > Battery so it can wake for incoming calls. Keeping the app allowed to run in the background is what restores the incoming-call screen. See how others solved this on Reddit

It can still handle WhatsApp messaging, calls, and light browsing, but the aging Android version means newer app features and security patches are gone, and a worn battery will struggle. Replacing the (removable) battery is a cheap reliability boost, and you can clear space under Settings > Storage > Cached data and uninstall heavy apps to free RAM. For WhatsApp specifically, keep the app updated as long as the Play Store allows, since support for this Android version is being phased out. See how others solved this on Reddit

Years of cached data and background apps are the usual culprits on the S5 Sport. Clear WhatsApp's cache via Settings > Applications > Application manager > WhatsApp > Storage > Clear cache, speed up the UI by setting the window and transition animation scales to 0.5x (or off) under Settings > Developer options, and reduce media auto-download in WhatsApp's own Settings > Storage and data. If it stays sluggish, a factory reset after backing up your chats to Google Drive often restores noticeable speed. See how others solved this on Reddit

Power it off immediately, pull the removable back cover and battery, and remove the SIM and microSD so nothing corrodes. Dry everything with a towel and let the parts sit in a sealed container with silica gel packets for a day or two (rice is a last resort and leaves dust); do not charge or power on while damp. Once fully dry, reinsert the battery and boot it, then re-check WhatsApp and your messages after confirming the screen and speaker work. See how others solved this on Reddit