Zain, auto negotiation is where 2 interfaces decide what speed and duplex they will will communicate at. Half duplex means that the interface will send/receive packets in both directions but not simultaneously. Full duplex means the interface will send/receive packets in both directions simultaneously. If you disable auto negotiate on a switch interface, you will have to disable it on the connected device as well. The configuration must match on both interfaces.
How to disable auto negotiate:
Configure port auto speed duplex
Hope this helps.