ok, can you tell me what version of safari you have.
i have read a few support threads on the smf forums and they're all rather short. basically smf wiping their hands of it saying its the users problem. it seems to be more widespread than a single user though.
other than that, i suppose what version of macOS are you running and maybe a speed test from speedtest.net or ozspeedtest.com or something and if you can, some ping results to antrx.com
just hide your ip address if you post up screenshots.
cheers.