I have tried 2 things :
1) Without firewall just my ssg5 ping still was 15
2) I pluged a laptop directly to ISP cable pass the firewall and ssg5 and then it was 40 more or less
So the fault is buried in ssg5 , I did not try to ping while there is no one left in the company so I will do it first thing in the morning see if there is any difference to it. Still is it possible that from 40 it can drop to 15 ? And why always 14-15 not 20-24 for example.