It make me crazy with mikrotik MTU

I’m use RB1100. I’m using Hotspot with FreeRADIUS. User an open all website(http) but it slow to redirect to yahoo mail, gmail, facebook (https site) and sometime pages can no open. what wrong with configuration? I think maybe the MTU problem, can anyone tell me.
I use mturouter.exe to find the correct mtu number. when i try comment mturouter.exe -t google.com it show message like “No response from tracerouter form this TTL. Tired 3 times” what the problem
ping.png
ping.png

You on DSL or PPPOE? Change MTU to 1492.