Thanks alot.What's a "Multiplexer"?
I expect that is the source of your problem. You need all 8 wires connected correctly in the cable for it to work at 1Gbps.
Don't mess around with the config. on the routers - it probably won't achieve anything. Auto should work.
How to do this ? https://www.youtube.com/watch?v=lxsBE7V17_A What are the steps that i should follow in mikrotik.Not by RouterOS.