Start with the speed test. If the download/upload speeds are within 10% of what you are paying for, then your internet is good.
Next, try a different browser. If it runs faster, then clearing the cache and limiting the number of open tabs on your current browser may help.
Then, the problem may be errors on your HDD.
The following are run in a CMD (command) window.
Run ***CHKDSK*** to see if there are any errors. search CHKDSK for instructions. I like to run it first without any switch to see if there are errors since it won't tell you if it found/fixed any errors when run on drive C:. If it finds errors, then I run it with the /f switch.
Then run ***SFC /scannow***. That will check system files for errors and most of the time fix them. If it can't fix all errors, then you need to run ***DISM.exe /Online /Cleanup-image /Restorehealth***
If it is not fast after all that, then try updating drivers. If using WiFi instead of Ethernet on a laptop, replacing the WiFi module with a newer version may get you faster.