Power runs thru the passenger side switch even when the drivers side switch is being used.
It could be either switch, easiest thing to try first is removing both switches, clean them out using electrical contact cleaner and compressed air. Also clean the contacts of the plugs on the wire harness. If that's doesn't work, further testing is necessary.
For slow operation, remove the door panels and inspect the regulator for looseness, being extremely dirty or gummed up and/or not having any lubricant. Clean as necessary and lube. If that's doesn't work, you will have to check the plastic rollers and roller tracks and the motors for being worn out.
Neither problem is hard or difficult, more time consuming than anything else.
Report back with your findings so we can assist further.