iPhone 5s software update downloading do not to supporting

I am not sure from your question what exactly is your issue but, let me try asking

But first note - Iphone5S can only be upgraded upto iOs 12.x - read more here: https://support.apple.com/en-gb/guide/iphone/iphe3fa5df43/12.0/ios/12.0

So now if you are connected to WiFi and on Power/Charging status - you can download and install. Without a WiFi and without 50% or more battery and sometimes required to be kept on charging station.

After download, you can install it.