After this update my whatsapp just works for 1 min and then it got struck … after closing the app it restarts again and same issue continues… due to this battery drain was also faster like 2 to 3% … I’vetried offload technique also but that also doesn’t work … what to do 
are you using any third party keyboards bro? is the iPhone have enough free storage to function normally? your iPhone model and current iOS version?