Website load slowly, not finding any problem

Hi, my website slow lately. How to confirm it in server site or wordpress site.

My website: https://www.bsenetwork.com/ (multisite with 16 plugin activate, 8-12 sec)

Another site on same Cpanel: https://bsenetwork.com/TestWordpressSpeed/ (vanilla, fresh install, 3.6s)

Another website same shared hosting, different cpanel http://www.globaltijari2u.com 1.6sec)

Im trying activate and deactivate plugin, but result same. This my latest perfomance https://gtmetrix.com/reports/bsenetwork.com/Ly7jdlzk.

Need help from Super Hero.. Almost 6 hour try figure out myself with hosting personnel, dont seem we know any problem yet.