Note: Ensure you are using the official 7-Zip, as fake versions can carry malware. To help you further, could you tell me:
Download and install the free software from the official 7-Zip site. Extract: Right-click the #BEST_15.7z file. Select 7-Zip > Extract Here or Extract to "#BEST_15" . Alternative Methods #BEST_15.7z
What are you using (Windows 10/11, macOS, Linux)? Note: Ensure you are using the official 7-Zip,
Use 7z x #BEST_15.7z -o./output_directory . Unzip One: A free alternative app on the Microsoft Store. #BEST_15.7z
What (if any) are you seeing when trying to open it? How to Use 7-Zip to Compress Files and Extract Files