You can only download High Sierra from Apple if you previously “purchased” it (free) under your Apple ID, or via official recovery modes on real Macs.
Downloading pre-made macOS High Sierra 10.13.6.iso from random torrent sites or file lockers is dangerous. These files are often modified with malware, rootkits, or cryptominers. Furthermore, distributing Apple’s copyrighted OS is illegal. Macos High Sierra 10.13.6.iso