Some ISPs (Internet Service Providers) "throttle" your connection if they detect a massive, sustained download. If you notice speeds drop off exactly after 20GB, your ISP might be the bottleneck.
Steam automatically picks a server near you, but that server might be overloaded. Go to Settings > Downloads > Download Region and try a different city in your country or a neighboring country. download a steam game faster
If you're playing an offline game while waiting, Steam pauses downloads by default. Enable "Allow downloads during gameplay" to keep progress moving. 2. Prioritize Your Network Connection download a steam game faster