A beginner question. I can't figure out where to file the teeth after watching Youtube videos. I'm attaching a picture of my Remington 14'' Limb N Trim, which doesn't really cut now. The arrow is the direction of the chain movement. I can't imagine the direction would be wrong because a few years ago the tool worked well and I don't recall ever replacing it. So, it must be the teeth. I want to try filing them first before I decide to replace it. Of the 4 points I mark, which point should I file? I didn't find a Web site that shows how the teeth of the chain saw do the cutting. Thank you!