If Whatsapp not able to update on google playstore, then search for “apkmirror whatsapp” from google crome download the latest version link this will solve the problem.
How to install WhatsApp APK Manually
After downloading whatsapp apk from apkmirror (before installing the download file check)
To install an APK, make sure you head into Settings > Security > Unknown sources and ensure the toggle is on. Then, press on the downloaded APK file and follow the instructions to install. It’s that easy.