It's great of you that you have come for advice, rather than diving right in and doing it incorrectly. To answer your first question: You should apply some pressure, instead of doing it to hard or soft. You can do this by: Doing a proper swallow and holding it. Something to remember here...keep the tip of your tongue on the incisive papilla.

Your second question: When you're mewing you will go through an ugly duckling phase that lasts a few months. The signs you're mewing correctly are that you're seeing an increase in palate width(this takes weeks to see about half a mm a week is gained), you find yourself with your tongue on the roof the mouth after you wake up, you don't catch yourself with bad posture, these are just few to name.

Thank you for helping me out but i think i need some explanation about this proper swallowing techinique.

I watched some Mew's videos and the way he shows it, i'm unable to breath if i wan't to keep this poistion at all times. If i try to breath in this position thrn i feel i need to push air thru some liquid while not feeling any pressure on palate anymore. 

Also how should the pressure be applied? In what direction etc?

Also do you like suck the back of your tongue into place? Or should the pressure be painful?

Are you aware the tongue sweep? If not learn about it. The swallow technique is when you tongue sweep and when you're swallowing you push your tongue on the palate up and forwards. Your problems with breathing is because of pushing the back of your tongue into your throat, avoid moving the back the tongue into the throat. I don't suck the back of the tongue, I use the swallow technique. I'm confused about the last question, if I'm right you're talking about tooth aches or some sensation in your throat. You should apply the pressure just good enough that you can keep your tongue up for a good duration of time comfortably. Push laterally, upwards, and forwards(get the back of the tongue involved). Just fiddle with your tongue long enough, so you can apply pressure on as many places as you can and breathe clearly.

Okay i think got the hang of it, now is overbite allowed or do i have to keep my teeth together?

So you have an overbite. Does it cause your teeth to misalign? As in your 1st molar doesn't line up with you 1st molar. Yes, you do have to keep your teeth together.