I thought it was thin plastic, but while testing it, I saw it was paper with some kind of coating. Sanding, priming, and then painting didn’t work well. I could easily scratch the paint off. Then I discovered the back doesn’t have a coating. I traced the drawing by building a light box with a lamp and a baking dish.
After that, I could paint, and I’m happy with the end result. Because the paper doesn’t absorb the paint as well as the wood, it was a bit more difficult to paint the small details.
Ahhhh you’re a genius! It turned out beautifully and I love the colours! They’re a perfect match to the swing ride I hope you make the entire amusement park series one day!
Thank you @Aiffah_Badron This is why I shared it. I thought it might be helpful for others. I did check if the pieces were symmetrical before painting, otherwise there’s a chance it won’t fit.
Thank you @JDisaduck I still have the parachute tower, a Ferris wheel, and something with airplanes. Just one more to buy and I’ll have the complete collection
the next update will have to wait a little longer, because painting will take some time 
this could be a great solution anytime i stumbled situation like this. The drawing came out looking perfect!
It turned out beautifully and I love the colours! They’re a perfect match to the swing ride I hope you make the entire amusement park series one day! 