1. I use a Google DNS. Your choice but many ISP DNS are just slow. If you are picky, you can test with (google it) NAMEBENCH.

2. I often find overreaching security suites. I use a bare browser with 2 addons.
a. Web Of Trust.
b. Ublock Origin.

3. After I've checked the PC for overreaching AV suites I reset the browsers, add my 2 addons and re-test.

4. You might be on WiFi. NEVER push the distance. Keep in line of sight and never let clients whine about how the router must be in the basement. Don't take on that job. Let another company do that and take the bad reviews on Yelp.