Okay, I did what you have said.
1. Downloaded RMXTools.
2. Extracted Remix OS ISO file to newly created NTFS partition.
3. Opened RMXTools
4. Set "New size" to 8Gb. then selected "Browse" - system.img - Create new data.img.
5. After finish moved that file to new partition.
ThanX for support. Waiting for your further guide.