WhatsApp for LG Stylus 3

Leave the phone plugged in, on Wi-Fi, and let it sit at 99% for 10-30 minutes, since on a slow device like the Stylus 3 the final step is decrypting and writing all the media before it completes. If it never finishes, tap the 3-dot menu in WhatsApp during setup to choose Skip, get into the app, then go to Settings > Chats > Chat backup to retry, and make sure the Google account holding the backup matches the one signed into Settings > Accounts on the phone. See how others solved this on Reddit

This is Android battery optimization freezing WhatsApp in the background, so go to Settings > Apps > WhatsApp > Battery and set it to Unrestricted (or turn battery optimization off), then allow background activity. Also disable any Power saving / battery saver mode and confirm WhatsApp notifications are on under Settings > Apps > WhatsApp > Notifications so messages arrive without you opening the app. See how others solved this on Reddit

Free up storage first, since WhatsApp slows down when the phone is full: open WhatsApp > Settings > Storage and data > Manage storage to delete large videos and forwarded media, and clear the cache under Settings > Apps > WhatsApp > Storage (clearing cache won't delete chats). Back up to Google Drive, then uninstall and reinstall the latest WhatsApp from the Play Store to clear out bloat that built up on the older Android version. See how others solved this on Reddit

On newer WhatsApp versions the media moved from the old Internal storage/WhatsApp path to Android/media/com.whatsapp/WhatsApp, so use a file manager and browse to Android > media > com.whatsapp > WhatsApp > Media to find your photos and videos. If you're moving to a new phone, copy that whole folder into the same Android/media location on the new device. If you don't see the files, enable 'Show hidden files' in your file manager so the full folder contents appear. See how others solved this on Reddit

WhatsApp has been dropping support for older Android versions, so check Settings > About phone > Software info for your Android version, then update WhatsApp in the Play Store while it still installs. If you keep hitting crashes or can no longer update the app, your best move is migrating to a newer budget Android - back up to Google Drive on the Stylus 3, then restore on the new phone using the same phone number and Google account. See how others solved this on Reddit

Keep WhatsApp and the Play Store updated, set WhatsApp's battery usage to Unrestricted under Settings > Apps > WhatsApp > Battery so notifications stay live, and turn off LG's Smart cleaning / memory cleaners that kill background apps. For media-heavy chats, set WhatsApp > Settings > Storage and data > Media auto-download to Wi-Fi only so the Stylus 3 isn't constantly downloading and filling its limited storage. See how others solved this on Reddit