Ensure you have downloaded every volume of the archive. For this specific file, you likely need at least a part2.rar . If any part is missing, the extraction will fail.
This usually means one of the parts didn't download correctly. Try redownloading the specific part mentioned in the error message. Alexandra-1.0-pc.part1.rar
Ensure all parts are named exactly the same (except for the part number) and are in the same folder. Ensure you have downloaded every volume of the archive