i have this black faces and i use many way but with no result
(i used recalculate and flip faces - ctrl + n // ctrl + n +shift )
Your model has very irregular topology containing ngons which causes this weird shading
and any solution
i imported the file from skechup
i suggest cleaning up the model: removing doubles, ngons, it should start to look correct!
N-gons, overlapping faces and extra verticies are giving you the headaches. I tried several approaches and found in the end, rebuilding parts fared much better.
even though sketchup lets you make faces with holes, it is in fact illegal geometrically.
using quads is good practice, even outside blender.
sketchup can be finicky, be sure to check your model with a fine tooth comb for double faces or stray lines.
some importers will give you custom normals, be sure to ditch those in the mesh properties, under geometry i believe.
NOTE: i have not been able to check the blend.
thx all i try to export to 3ds and it’s work 