More likely than not, this issue is a result of too many people trying to download it all at once, so the worst case scenario is that server strain should lighten up within a few days, finally giving players the chance to experience the story and gameplay of Genshin Impact. Version 1.1 of Genshin Impact introduces four new characters to play as, but theres still plenty to look forward throughout the remainder of the year. Other than these things, players should make sure they have a strong internet connection and are using an ethernet cable for wired connection if possible.
With any luck, Genshin Impact developer miHoYo will fix this issue soon so that players don't have to jump through hoops to play its game, but the developer has not made any comment on the issue yet. It's currently unclear what is causing these terrible download speeds, but it is likely something server side given how many people are experiencing issues. While the best resolution to enjoy Genshin Impact is 19201080, players can set it around 1280720 to increase the FPS in the game. By decreasing the graphic quality, players can trade it off for a faster gameplay.
Use an online speed check to ensure that your broadband gives a download. On the same principle, closing out of the launcher entirely and reopening it seems to have positive results for some, and if even that doesn't work, players may just need to delete the application and start the download over again. You can optimize the in-game graphics settings to reduce the lag in Genshin Impact. In most cases, a slow download speed is because of a poor internet connection.