Download the 1.5 GB demo via Steam. If you enjoy it, you can purchase the full game. Steam will not re-download the entire 7 GB. It will simply unlock the full game and download an additional 500–800 MB of missing assets. This is the closest you will get to a "500 MB download" for the full experience.
Individual game patches or minor updates are often around 500 MB in size. Legacy Version: The very first Euro Truck Simulator (released in 2008) had a much smaller footprint of roughly Minimum System Requirements euro truck simulator 2 download for pc 500 mb