With a slope into the garage all you’ll end up with is a bigger step further into the garage. It might be dry but it’ll d next to useless as a garage need a 4*4 just to get in and out.
Proceed with caution.
Looks like that concrete has a slope on it already
I’d be tempted to think about lowering the drain and chopping out the concrete and relaying it to a lower level back out to the drain from the door level.
Should end up with only a small step at the drain.
Obviously check my assumptions with a string an level before taking action.
Obviously previous owner or his trademan doesn’t know how hid string line works