Download and install a free extraction tool like WinRAR or 7-Zip .
After extraction completes, you will find the actual update files for your game. Baldurs.Gate.3.Update.Holy.Knight.part05.rar
The file Baldurs.Gate.3.Update.Holy.Knight.part05.rar is just one piece of a split multi-part WinRAR archive. You cannot extract it on its own. Download and install a free extraction tool like
Split RAR archives require every single segment to be present in the exact same folder to successfully combine and extract. You cannot extract it on its own
Open the newly extracted folder to find the game files (often containing a bin or Data folder).
Look for all accompanying files named part01.rar , part02.rar , part03.rar , part04.rar , etc.
To use the files inside Baldurs.Gate.3.Update.Holy.Knight.part05.rar , you must place all numbered parts ( part01 through the final part) in the exact same folder and extract only the first part ( part01.rar ) using an extraction program like WinRAR or 7-Zip.