Cant change resolution to 1920 x 1080

He/she is asking about which mode you choose to use the second monitor as, cloned image or extended desktop?

In cloned mode you see the same on both displays (laptop and monitor) in extended the two (or more) displays show different parts of your desktop and you can for example move your pointer from one to the other.
If you are using cloned mode the max resolution will be the resolution of the display with the smaller available resolutions.
But you can also check whether the driver correctly identifies your external display otherwise you might need to override it.
It would be nice if you told us the model of your laptop or at least the type of graphic chip it has.