Hello,
If everything is correct, multiple instances of ConHost shouldn't be open; usually, only one or two remain open in the details tab.
Did you run MSRT, Malwarebytes, and AdwCleaner scans to check for malware?
https://www.microsoft.com/en-us/download/details.aspx?id=9905
Have you downloaded any pirated software or games?
As a last resort, it would be good to do a complete and clean Windows reinstallation as a precaution if nothing is found.
Do the slowness problems occur at any time during use?
Open the command prompt (admin) and run the commands: sfc /scannow and dism /online /cleanup-image /restorehealth, wait for the process to finish and restart the computer.
Then perform a clean boot and if you want to uninstall applications that you do not use.
Perform an offline scan using Windows Defender > Open Windows Security > Virus & threat protection > Scan options > Offline scan
Thanks