Resize system partition?
Don't even start this without a solid backup.

Right click the NTFS partition &amp; select Move/Resize Partition.
Drag the Free Space After slider all the way to the left.
This will move the NTFS partition to the end of the disk &amp; the free space into the area outlined below, between the APFS container &amp; NTFS partition. This should then consolidate your free space.



Volumes on APFS containers will not show as filling all the available space, due to their 'live expandability' feature, even though the container itself does. I don't have an example with APFS &amp; NTFS to show, but this is my 1TB SSD which shows as having 456GB 'free' at the end whereas the container itself &amp; in the Finder the Volume is actually [almost] the entire 1TB.



So, to complete your changes, you need to select the APFS Container [not the Volume on it] &amp; again using Move/Resize Partition, change the New Size until it fills your moved Free Space.



Remember to Apply Operations afterwards.  

Note: This is likely to be a very long, slow operation; whilst potentially a lot faster on SSD [on which I have never actually tried to do a data move of this size] on HD I'd expect to come back to it in the morning, so make sure you have plenty of time &amp; keep the Mac on mains power.