Pnthg4-g891080.part4.rar -

You can force extraction to save whatever data was in the parts you do have.

starting from the first part. When WinRAR or 7-Zip encounters the "fake" part 4, it will likely show a "CRC error," but it may continue to extract subsequent parts. PNTHG4-G891080.part4.rar

If you are missing of a multi-part RAR archive, you cannot "generate" a functional replacement piece from scratch. Multi-part archives contain unique, sequential data; if one part is missing, the entire extraction will fail because the data stream is broken. You can force extraction to save whatever data