constant lag on 2g, and cant connect to 5g

I am having a bunch of connection issues. I used 5g for everything and then one day I just got disconnected from it and it made me use 2g. I was constantly lagging on 2g. When I tried to connect to 5g it said that the password was wrong even though I checked it and it was right. I didn't change a single thing except for WAN settings, LAN settings, and port forwarding settings. I set a static IP address to my xbox and then made it a DMZ server. Other than that all I did was port forward games for steam. I didn't do anything else and 5g still does not work. When I watch things like Youtube and Twitch it constanly buffers and wont stop. I don't know what I did, but I do know that it had nothing to do with the settings I changed because I did that about a month or so before I started having this problem. Thanks for the help