Tire over inflated and went flat? I thought my tire pressure was low.  I pumped air to the maximum resistance and after four hour there was hissing of air continuously while I was asleep and it woke me, how can I fix it?

It's a new one, bought three weeks ago and it's only the front tire went flat.
A puncture. Maybe a bit of glass still stuck in the tire. The tire had already lost air then when you pumped it up it got worse. 

Assuming it's a tire with a tube, you can get a tire patch kit or buy a new tube. If you're going to patch it, take the tube out, inflate it and locate the leak. Stick it in a bowl of water and look for the bubbles if it's hard to find. Mark it with a pen. Then let the air out, scuff up the area of the hole with a little sandpaper and follow the directions that came with your patch kit. 

Very carefully inspect the tire. Feel the inside all the way around. If there's any grit in there, that's bad. Inspect the outside carefully and look for a cut and maybe a bit of glass still stuck in there. If the damage is very minor you can keep using the tire, but if it's a bigger cut, it's better to replace it.

Inflate the tube just slightly when putting it back in the tire so it doesn't get twisted. If you have it, put baby powder on the tube before putting it back in it will help it get seated nicely.