iTunes sync iPhone takes forever...

latest version of iOS (12.0 (16A366)) and iTunes (12.9) and I started back-up but not finishing.

It takes forever? is it usual? Or do I must use Mac PC for back-up?

How to make back-up and sync in shorter time?

iPhone7+, and available volume is 80.00GB within total 128GB. only 48GB back-up!!