i'm mining with bitminter client with my GPU that is an "ATI Radeon Caicos PRO Prototype" with a speed of 20Mhps.. how long does it take to make 1 bitcoin mining this way

does it worth it?
At current difficulty, if you mine in a pool, you will probably mine about 0.00001406 BTC per week. That means, if difficulty doesn't increase at all, it will take about 71123 weeks (about 1367 years) to mine 1 BTC. Of course difficulty will almost certainly increase during that time. As such, it is quite possible that it will take more than 6000 years to mine 1 BTC.
or how to easily get bitcoins fast for free??? i don't wanna buy bitcoins...

In case you hadn't figured it out yet, bitcoins are money. As such, what you are saying is:
"How to easily get money fast for free??? I don't wanna earn money...

"
There is no magic here. You give something of value (product, time, service, etc) and in exchange you get something of value (bitcoins). That's the way the world works.