How to level this area of my garage?
I have the identical problem. It wouldn't be practical to try and alter the slope. You'd need a significant quantity of material, it would need to be expertly applied, and it will have a tendency to pop loose over time. 

I plan on cutting in several trough drains in strategic locations. They'll be something like this: 



I'll rent a concrete saw, make the cuts, dig down 6" or so below the slab and install pea gravel (to slightly increase drainage capacity), then set and anchor the drain kit. This will allow small amounts of water to collect and percolate into the soil inside the garage, which should mostly remain thawed. 

I plan on oversizing the cutouts a bit so I can anchor the drains in new concrete. I'll then epoxy the entire floor. 

In your case, I'd probably install the drain crossways right through that deeper puddle. This will serve to intercept flowing water as well as drain any that manages to get around to the back side. It'll also keep the drain away from vehicle traffic. They're designed for it, but your anchoring would have to be done very well.