All parts must retain their exact original file names and be placed in the identical folder or directory on your hard drive.
Many archival files from independent networks require a password to extract. These passwords are typically provided by the original uploader on the page where the download links were hosted.
This is the file extension for the Roshal Archive compressed format. RAR files compress data highly efficiently and support multi-volume (split) archiving. How Split RAR Archives Work
Then it stopped.
Always run an up-to-date antivirus scan on downloaded RAR files before extracting them.