well, I bought the computer version. And then found out that there's also a version for your android device. So there's no way that i can get the app from the store free? Or do i have to pay again?

The android version is separate and is only available on the Google Play Store, so yes, it needs to be purchased separately.

There is also a free version which you can try to see if it works on your setup.

https://play.google.com/store/apps/details?id=com.Freeride.Freerider

https://play.google.com/store/apps/details?id=com.Freeride.Freerider_FREE