do you know wich option do i have to enable/disable to make it look good?
loadout not showing well
You mean the render model? Pump up the graphics!
I think youll need to pick one of the “presets”, i dont quite understand why but i cant find individual settings for textures, shaders and so on. So your best option is to pick HIGH preset and then tune down what you can! 
And if get low fps, then fetch a nice potato config, there are some out which are just for this purpose! (looks at google)
You definitely should look at turning on some of the lighting effects, your dark background and lack of shadows on the model suggest that you have most of those off.
I asked about it on reddit a few days ago. Apparently no one exactly knows what to do. All I could do with previews is to make them bright by turning on all lighting options but the black background still remains. I tried to turn on everything, even world details were set to high settings, but nothing has helped.
Yes, was written quite often here if you browse the forum. HighQualityMaterials and HighQualityModels.