Wow, that is really, really bad! That is a good first lesson, if your slicer software shows missing parts or errors for your item that means those errors will continue to be present when it is printed, so it's important to always correct those before printing.
To try to correct the errors I would try these steps:
1. Redownload the file from here
2. Try loading the model in Cura, and make sure you have Generate Supports selected. If the errors are gone that is good.
3. If the errors are still there try running the model through this 3D fixer, then load the repaired model file in Cura and see if the errors are gone
*Please Note* I don't think there is anything wrong with the model, but the fixer is a last ditch method to see if the model will work with your Cura software
4. If the errors are still not fixed you might need to accept that your Cura software has some shortcomings. This was the case with my DaVinici 3D printer XYZ software so I purchased Simplify3D software and have been extremely happy with it.
Wonderful , after repairing the model through 3D fixer , all is working fine ....
Thanks for all , good job