Hey there!
I want to design a 3d printing part for the dashboard of my golf 6, more precisely the top middle part right 
.
I am somewhat experienced with designing parts in fusion 360 for daily usage, but I don't really know how to design this part.
I did try getting a fit for the front arc and an arc from the middle front to the middle back, then did construct a plane from both arcs and did round the result on both back edges. But I noticed when trying the fit, that the dashboard top is not really symmetric, but has an additional bump to the left.
Do you have any tips/guidance/ideas on how to get a better fit? I did think about scanning it 3d with some lidar device, but I don't have an iPhone and wouldn't know where else to get a device.
Get some childrens playdough, use something rigid like a 3d printed flat box to get the shape negative. Now you can use silicone or sth similar to get the exact shape and attach that part to the piece you actually want to attach. Perfekt shape even for weird geometries, also you can simply change the part that actually needs to be there with out any issues.
I think I will get some modeling clay to get a negative of a shape, if I can't get my hands on some iphone. Then get measurements from the negative.
Exact iPhone models should be easy to find online
Not talking about getting a negative of the iPhone lol :D The iPhone can 3D-scan stuff, I would like to try it for this use case.