Could somebody explain me how idle should behave. I am really confused what is going on my truck (manual). (I just bought it)

Cold engine - 1500-2000 rpm 1-2 mins
than drop to 600-800 rpm.

During driving when car in move it holds about 1500-2000 depends what engine speed was before pressed clutch pedal

After car stop. in 5-15 sec it drops to 600-800rpm.

Is this ok?