Welcome to OSM and thanks for editing!

Just a few suggestions:
1. When the parking lot is more or less rectangular you can press Q key to automatically force all its angles to 90˚. Those shapes then look much nicer.

2. You can try to add more nodes/point to the parking lot outline to make it shape more accurate. And try to avoid overlapping its area with other objects such as buildings. As an example you can look at this parking lot: https://www.openstreetmap.org/way/341662678

Cheers