So while it is totally possible to rollback to a previous software version, do try clearing the cache of your phone. But please describe the issue you are having. Are you unable to open apps or do they crash while on WiFi or...? Does the issue persist if you use your mobile data or use another WiFi network?
If you're experiencing Wi-Fi or network connectivity issues on your Galaxy device, you can reset all the network settings to their defaults.
If the problem persists, we suggest you to do wipe cache partition on your phone as suggested by@CHMultimedia.
>> Switch off the phone using the power key >> Press and hold Volume up and power key at the same time for 1-2 minutes>> Release the keys once you see the Samsung Logo >> Press the Volume up button to get into the recovery mode >> In recovery mode, use the Volume keys to navigate between options >> Select “Wipe Cache Partition” >> Select “Yes” >> Reboot the device once the wipe cache partition process is complete. I hope it will solve your issue.
(Note: Wiping the cache will NOT delete your apps or your data or your configuration).