This is not a big file, i wonder about.
RC Felge_Raphi_V14.stl (1.6 MB)
Try this file with high settings and a scale of 500%, my pc took about 1 min to slice, generate and preview gcode.
8x 3,9Ghz 32GB RAM WIN10 latest
Have a look at this thread, which shows your 300kB stl size should be peanuts: