Here are some steps to resolve the issue of slow internet browsing even when speed is fast enough.
1. Make sure your browser is up to date.
2. Run Ccleaner (free) which does a good job of clearing out cookies and cleaning out the cache.
3. Try updating LAN & Wireless Drivers. (Device Manager >>Network Adapters>>Right Click Wireless/LAN Driver>>Update Driver Software)
4. Open Browser Press (CTRL+SHIFT+DEL) together for Chrome, Firefox & Internet Explorer Browsers. Tick on the things you want to delete
such as History, Cache, cookies, form data, etc. Select the time from when you want to delete. Click on Clear Browsing history.
5. Install good antivirus and scan the system for any virus, malware, adware, trojan,spyware,etc. Clean them all.
Contact good technician in your area who are capable of resolving such prolems.