Why am I having trouble downloading the latest update it says there is a network or server error
easiest way is to just call your carrier (chat using their chat services if that's your preference) and ask regarding the network or their server, mention that you are having issues updating.
If they say it's not their side's issue, then you could either try to update again and when it fails to update... submit an issue report to Samsung Members app. OR backup your data and flash to a new software either by asking your carrier, the UbreakIfix repair center, or DIY at home using Odin.
DIY will void your warranty tho, so ask the mentioned above services first.