You must have parts of the archive in the same folder. If the set has 10 parts, you need files named part1.rar through part10.rar .
If a window pops up asking for a password, you must find it from the original source where you downloaded the file. Cbrl-021.part7.rar
To open a file named Cbrl-021.part7.rar , you are dealing with a . This means the original data was split into several smaller pieces to make it easier to upload or download. You must have parts of the archive in the same folder
This usually means one of the parts (possibly Part 7) is corrupted. You may need to download that specific part again. Cbrl-021.part7.rar