WhatsApp for Samsung Galaxy S6

On the Samsung Keyboard, the Enter key is set to send the message in WhatsApp. To add line breaks, change the Enter key behavior: open Settings > General management > Samsung Keyboard settings, and turn off 'Send messages with Enter key' (or its equivalent toggle). With that off, the Enter key inserts a new line and you send with the on-screen send arrow instead. Alternatively, install Gboard from the Play Store, which keeps a separate return key. See how others solved this on Reddit

Yes. As long as your Galaxy S6 has an active SIM with a real mobile number that can receive SMS, install WhatsApp from the Play Store, enter that number, and complete the verification code it sends by SMS (or by voice call). WhatsApp only needs the SMS or call once to verify the number; after that it works over Wi-Fi or mobile data and does not rely on SMS for ongoing chats. See how others solved this on Reddit

WhatsApp Web is built for desktop browsers, so Samsung Internet serves the mobile site and won't show the QR pairing screen on a phone. Tap the menu (three lines) in Samsung Internet, enable 'Desktop site,' then reload web.whatsapp.com. If it still fails, clear the browser cache under Settings > Apps > Samsung Internet > Storage > Clear cache. On a phone the supported option is just to use the standalone WhatsApp app rather than WhatsApp Web. See how others solved this on Reddit

One UI's battery optimization often freezes WhatsApp in the background. Go to Settings > Apps > WhatsApp > Battery and set it to 'Unrestricted.' Then under Settings > Apps > WhatsApp > Notifications, confirm notifications and the message channels are turned on. Finally, in Settings > Battery and device care > Battery, turn off 'Adaptive battery' and remove WhatsApp from any 'Sleeping apps' / 'Deep sleeping apps' list so it can deliver alerts in real time. See how others solved this on Reddit

WhatsApp's phone layout doesn't always resize cleanly in DeX's resizable desktop window, which can cause freezing and glitches. Try running WhatsApp in a fixed, phone-sized window instead of maximizing it, and clear its cache via Settings > Apps > WhatsApp > Storage > Clear cache. If you mainly need it on the big screen, use WhatsApp Web or the WhatsApp desktop app linked to your phone, which is more stable in DeX than the resized mobile app. See how others solved this on Reddit

That is WhatsApp's two-step verification PIN, not your device lock screen. Enter the 6-digit PIN you set up earlier. If you've forgotten it, tap 'Forgot PIN' to get a reset link sent to the email address you added under WhatsApp Settings > Account > Two-step verification; if no email was registered, WhatsApp makes you wait 7 days before you can reset and sign in again. If the app itself won't launch at all, update it from the Play Store and clear its cache under Settings > Apps > WhatsApp > Storage. See how others solved this on Reddit