My left analog stick is not working properly

sharpluck, sounds like a bad stick. I would suggest to replace the stick with a set of new ones. They are relatively inexpensive and it only requires basic soldering skills to replace them. You can also try to reflow the solder connections of the joystick. If that does not help it may be time to "replace the controller. They are available on places like this. On the how-to part, here is my answer from a similar question. "use this as a general guide. All you need to do, is to unsolder the connector and solder the new joystick in place. It should be a straight forward repair. Of course, you'll need a soldering iron, a desoldering wick (or solder sucker, flux and solder to repair the joystick...Hope this helps, here is a great tutorial. hope this helps, good luck.