Question Router Configuration Slow speed


Nov 15, 2018
I am a noob so please bear with me.I have an ISP provided dual band router (2.4GHZ and 5 GHZ). My problem is I am not getting the maximum speed (100 Mbps) according to my plan and my ISP is not very helpful.

I get almost full speed on my wifi 5 GHZ connection on my new cell phone. But my ethernet connection gives me only like 80 Mbps(I use to get nearly 100 Mbps with my previous single band 2.4 GHZ router). I am trying to find if I can change some settings on my router which could increase the speed for my LAN connection (attached pictures of my router configuration pages).

My question is: On Local network configuration page I see LAN Configuration Mode.
If I change any of these options can I improve my speed:
which has options of -> "Manual", "Automatically Configurate Prefix and DNS server" and "Automatically Configurate DNS"
I have set it to
Primary DNS Server:
Secondary DNS Server: 2606:4700:4700::1111
(This is what I filled which I found on the internet- DNS addresses. I cant fill in IPV4 addresses though my selection is IPV4/IPV6. Don't know why?).
Can I improve my speed with manual configuration?
On Manual I have to fill in:
Prefix: (which I don't know what to fill)
Prefix Length: (which I don't know what to fill)
*[16 - 64]
Primary Time:3600 (already there) *[60 - 4294967295 S]
Lease Time: 7200 (already there)
Primary DNS server Secondary DNS server

Question Number 2: Under NET -> Internet connection -> I see an option called "Binding option" which has boxes for LAN 1-4, SSID 1-4, SSIDAC 1-4
What is this for? Does checking anything of these help.
Thank You for your help.