Well, mask clearing issues are one of the most common problems that new open water students have, so you are not alone! The good news is that you can do a lot of practice to fix this in your kitchen sink or bathtub.
The first step in mastery of mask problems is to learn to control whether your breathing goes through your mouth or your nose. If you are sucking water in from a flooded mask, you are allowing yourself to breathe through your nose when you shouldn't; this is actually pretty easy to fix. Try this exercise: While you are sitting and reading this, put your hand over your mouth. Inflate your mouth so your cheeks puff up. Now, without removing your hand, let the air out through your nose. Then refill your cheeks, and let the air out through your nose. Repeat this until you have identified the change you make in the back of your throat to reroute the air -- this is airway control. Understanding this will make sure you never try to inhale or exhale air where you don't want it to go.
Now, fill your sink with water, and take your snorkel in your mouth. Put your face in the water, and breathe through the snorkel without any mask at all. If you draw air in through your nose and choke, stand up and practice the nose/mouth rerouting exercise again, and then retry. Eventually, you should be able to breathe through the snorkel with your bare face in the water without any difficulty.
Now add the mask. Put your face in the sink, and fill the mask with water. Breathe through the snorkel with a flooded mask. Then lift your face OUT of the water (keep your head over the sink, or this will get messy). Put a finger on each of the upper, outer corners of the mask, and very gently exhale through your nose. Do NOT blow or snort; just exhale as though you were breathing normally. The water in the mask will run out of the bottom, and I can guarantee you that, if you exhale slowly and gently, the mask will be empty before your lungs are
Once this exercise goes well in the sink, try it in the bathtub, lying on your stomach (if your tub will allow that). Don't lift the head entirely out of the water, just go from looking straight down to looking straight ahead. By now, this should be easy.
If you tilt your head back so that the plane of your face goes behind the vertical, water will passively run down the base of your nasopharynx and into your throat. This is a big mistake students make when they are doing their skills in a seated or kneeling position, where their face is already vertical. The instruction to tilt the head back is for a diver who is horizontal in the water, and looking down; that person needs to tilt the head back to get the bottom of the mask to be the lowest point. That is NOT necessary when in an upright position.
Try this, and come back and tell us how it went!