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I got the models from https://www.thingiverse.com. And i spend a couple of days to test different settings to get a decent result. I dont have the knowledge right know to design my own models.
But as I know you can use any CAD (cumputer assisted design) programm to create suitable models to print...

your answer is already helpfull i already have Seen some CAD Tutorials before But did Not Know that you can User them for 3D Printer.

Yes you can. But I dont know if you need to convert the files into another format. So the slicer can convert the model into g-code.