Seems like I have air or water behind liner. I drained the pool and there seemed to be air or water under liner/probaly water. In filling back up 1/2 full the water behind liner is at the same level. How will the water get out as it gets full

You will need to pump the water out from behind the liner. Find a pump that has a relatively small suction hose that you can slide behind the liner.

Or a wet/dry shop vac