When starting, your alarm will go off when your air tanks are at pressure and you'll hear it blow off. Meaning your tanks are full. Then switch the air bags lever to auto. It will (should) then inflate your air bags. By going outside you can visually confirm the coach is raising to ride height. Again, when the tanks reach pressure it will blow off and the coach should be aired up. Visually you should be able to determine this.
As others noted you should learn to test for leaks as some of your other comments lead to believing there is a issue if deflating while driving.
The air dump lever should be dumped before extending your jacks ( at least in ours). But we have the hydraulic system, other manufactures and higher end coaches use a air system to level if you have that. I always dump the air when not driving and parked for some time.
Starting your engine and run time is another thread all together. But most of what you hear is long enough to pull in your slides, retract your jacks, and inflate your air ride. Some coaches have a different procedure, but the engine must be on in ours to bring the slides in or operate the hydraulic jacks.