Thank you for reaching out. I can certainly understand your concern with your Whatsapp clone immediately crashing, and I would be happy to look into this further for you. First step I would recommend would be clearing the cache for Whatsapp. Go to settings > apps > Whatsapp > tap on force stop then storage and clear the cache.
Next step would be to uninstall and re-install Whatsapp. This will help rule out any software symptoms or an update that may not have pushed through completely.
Third step would be to wipe the cache partition. The system cache partition stores temporary system data. It's supposed to allow the system to access apps more quickly and efficiently, but sometimes things get cluttered and outdated, so a periodic cache clearing can help make the system run more smoothly. You would also in this menu want to repair you apps.
If you have tried all the troubleshooting step to this point, the next step would be a factory reset. This will take your device back to the stock setting out of the box. Make sure to back your device up prior to factory resetting. Give this link a try for the steps to factory reset your device: https://www.samsung.com/us/support/answer/ANS00062029/
