Can i use the USB-C charger to charge an iphone xs max

The iPhone XS came with a 5W power adapter and a Lightning to USB cable.

There is absolutely no reason why you cannot use a Lightning to USB-C cable and a larger power adapter.

Also see: Fast charge your iPhone - Apple Support

It is recommended that you use the original Apple cable and power adaptor that came with your iPhone. You can charge via a Lightning to USB or Lightning to USB-C cable. You can also use any third-party cable that is compatible with iPhone.

Yes.