Here's the part where many people get the wrong movement going. You're not trying to push something down the drain. Exactly what you want to do is produce suction that will dislodge the obstruction. Push down firmly on the plunger till the cup is pushed against the drain. Now, BOUNCE the plunger vigorously without pulling it off the drain. You'll hear water sloshing as the suction yanks on it. Bounce for several seconds - you'll feel the suction 'getting hold of' at the plunger.
Prior to you in fact work with a Plumber, often it is a good idea to set up a preliminary conference with a plumbing professional to check them on whether the Plumber is on time. The last thing you wish to do