Starting my first game

I’m starting the creation of my first real game, made from scratch by me. The first thing I want to do is this:

I’m basing it of this image. It’s a 2d game, but not exactly something, from what I know, that can be entirely done in paper2d, cause it’s not about platforming. I want to give a 3d angle to the game, where theres multiple tiles that you can move across. Something like this:

Pressing the up and down keys you move from road to road, each road being separated by the black lines. If I place an object over the top road, you won’t be able to go there, in the case of this image, the white pillar.

I’m starting off really simple, using only a ball as the main character and separating each lane in a different layer, in the PaperTileMap asset. But I honestly don’t know what to do, even with the physics, cause to create this kind of camera I would have to place the characters in a way they would fall off the map.
I hope you can understand what I want, the more tips you can give the best, sorry for being time consuming.