The .part1 suffix indicates that this is a split archive (usually created with WinRAR or 7-Zip). Critical Download Instructions
Once all parts are downloaded, place them in the same folder. Right-click on Part 1 and select "Extract Here" using a utility like WinRAR or 7-Zip . The software will automatically pull data from the other parts to recreate the original video file.
Files from third-party sharing sites like 5156share should be handled with caution. Ensure you have an active antivirus scan running, as these types of community-uploaded archives can occasionally contain unwanted scripts or adware bundled within the compression.