I do use nearest
The problem is not the game 'engine', but give the 'correct' image so it can 'scale'.
As you can see, I can solve this by converting the image in Photoshop, and create hard edges and lower the colours.
I though maybe there is some converter on the internet that can do this for me.
As I know now, I can use the photoshop filter: Posterise and cutout, and than do the things manual.
Going to invest some time in pixel art 'rules'
https://www.makeuseof.com/how-to-make-p ... ers-guide/
Single pixels, or a group of pixels that break up the consistency of a line, are called "jaggies." Jaggies are exactly what we're trying to avoid.
Maybe I can find a program that convert the 'Jaggies' into correct lines, but I guess I have to do this manual.
Thanks for all the info.