You should go to the SPEEDTEST.NET speedtest.net free Internet speed testing site and test each of all your browsers such as IE11, Edge, Chrome, Firefox, Safari, Opera, etc. They should all be getting approximately the same speeds. If one or all of them has significantly lower speeds, then those browsers are most likely broken and need to be repaired individually which often requires uninstalling/reinstalling them (make sure to disable your AV prior to trying that). There are a couple of browser repair tools available free from Microsoft called "MICROSOFT FIXIT", but in my experience they rarely produce a corrective result across ALL browsers if they have slow Internet speed above 30% speed reduction.
If all your browsers are producing results less than 70% of your current rated speed (less than 60Mbps), then you can consider repairing Windows as you can't really fix IE11 or Edge browsers as they are built into the Kernel of the W10 OS. You could also be having speed problems due to a virus infection (have you run your antivirus and scanned your entire computer?). Also, Windows registry corruption problems can create this problem; that can be fixed by various windows repair tools which we have on the forum you can use (CHKSDSK, SFC, DISM, etc.) just search on those here using our search feature. If those don't work you need to look at testing your hardware, use this link: Windows 10 - Unclickable Task Bar. If your hardware testing passes, or if it didn't and you had to replace failed components, re-run the tests until they all pass.
At this point, you can attempt to do more advanced windows repairs such as running in-place upgrades, resets, and windows reinstallation variations. That link is embedded in the above post I linked to, but is also here for your convenience: recommended solutions are covered in my POST #3. Here's the link: Sound Problems.
***WARNING:we strongly suggest that you FIRST BACKUP ALL OF YOUR PERSONAL DATA TO EXTERNAL MEDIA! THIS WOULD INCLUDE YOUR LIBRARY FOLDERS FOR DOCUMENTS, PHOTOS, MUSIC, VIDEOS, AND ANY SAVED E-MAILS OR ATTACHMENTS IN ORDER TO PROTECT YOURSELF FROM IRRETRIEVABLE DATA LOSS!!!***