2003 GMC Envoy Oil Pressure up and water gauge lower

Hi
Help !
A week ago I smelled some burning and noticed oil pressure was past its' usual "straight up" normal.
Added oil and smell disappearred.
Oil pressure only slightly lower. It goes up with the speed, back to normal at idle.
And now, noticed the water guage is running lower.
The water pump was replaced at 71k miles.
What is happening?
cmdpp