Since you are downloading games from the Steam servers, you have to have an internet connection. If your Wi-Fi is poor, check if you have an ethernet port on your Wi-Fi router, which you can use to hard-line your PC for a better internet connection. If that fails (because you may live in a rural area), try going to a place that has an internet cafe. Be careful when using those; since they are not secure connections, but should be enough to allow you to download Steam games. There are tutorials online that show how to play Steam games in offline mode; which may be something you should look at since you need an internet connection to play the games you purchase from Steam.

Talk Doctor Online in Bissoy App