memory traffic log is 95% full" - Fortigate

Logging to memory will always consume over 90% memory after a short while - it was never meant to be a permanent thing. If your fgt device has a HD (or flash) you can try setting the logging to use that instead.  That being said, you really do not have to worry about logging to memory as the fgt should take care of "cleaning up" or freeing up memory.  If you have a FortiAnalyzer or other logging device, you could try logging to that instead if you need to logs. All IMO of course.

still not solve my problem very painful thing  i bought very expensive unit fortigate after time they error shows anybody please help me very quick and easy way to remove this error 

I have integrated Fortigate 60f with Forticloud. No local disk logging is enabled. I got these alerts I did log flush-cache but the alert is still showing. if error is resolved does alert disappear or it will be there in the dashboard.