took some photos in a dark setting, turned out extremely dark. how can i fix? (images provided)

Was the original shot in raw or JPEG?

Either way, the main problem is the way digital images are recorded by a camera sensor. Due to physics, the sensor devotes the most bits to store highlight data and the fewest bits for shadow detail, so in this original, practically all of the image information is down in the lowest quality bits in the shadows. This is why underexposure is so damaging to digital images.

Looking at the exposure data in the image, for a shaded scene like this, 1/2000 sec seems like too high a shutter speed for f/5.6 at ISO 400, so that’s probably why it got so underexposed. If the goal was to use 1/2000 sec to freeze the runners, a good strategy would be using shutter priority and Auto ISO together, to let ISO go as high as it (well beyond 400) after the aperture is maxed out.

For this image, you can try increasing Color Noise Reduction to see if that reduces the color artifacts, but it will be difficult to repair this.