hello, could you provide your latest few submitted crash reports? please enter about:crashes into the location bar, copy the latest few report ids from there starting with bp- & paste them here into a forum reply. this will give us a better understanding what may be triggering those issues.

i don't know know how to paste so i copied the last report 3/7/16 (bp-a4cb5997-c8c4-42e1-818f-de6172160308) This guy under the name- (drundleflyguy) in the answer site, he has the same problem i have, title headline is: firefox runs after close for more than 5 minutes. Thank you for your help.

thanks, this appears to be a networking-related shutdown-hang. there are some improvements in this regard in firefox 45, so can you please see if the situation improves once you update firefox?

Update Firefox to the latest release

PHILLIPP, I am leaving out of town for 3 days, i will be back with you when i return, thank you till then.