I am 26 years old , I live outside of the united states ........but here is the deal...I have a green card ( permanent one ) , I have finished 4-year college     ( PE) in my country with really good grades and good GPA( around  4 ) , I have never broken any kind ow law , in perfect health , never had any kind of surgery except for tonsils in the age of 6 , I have 20/20 vision....

I will be around 27 and 3/4 when I move to usa on permanent basis ,  so....

1.) what is my next step after that in order to become fighter pilot ( it doesnt really mater in which branch , as long  it is flying fighter planes )...and...

2.) what can I do in the meanwhile in my country in order to prepare myself better for that great , great achievment

thank you very much for your answers , truely

Your biggest issue will be citizenship.  You must be a US citizen at the time of commissioning.  Unfortunately, to become a pilot in the USAF you must be selected before the age of 30.  Unless there is a way to become a citizen and earn you comission before you turn 30, I doubt you will be able to fly for the USAF.

So , if I would be able to somehow resolve the citizhenship issue , I would be in much better situation , I presume , right ?

Yes, if you get citizenship and are able to complete Officer Training School before your 30th birthday, you could get a pilot slot (precluding factors I don't know about).

and how many flight hours should I take , also , what is the average cost of a flight hour
should I get my PPL , will it increase my chances

Yes, getting a PPL would help.  (That's not your biggest concern now.) 

To be a pilot of the U.S. Air Force, you must be selected before the age of 30. Unless there is a way to become a citizen, I wish you success.

Stay cool and positive and try to focus on what you really want in your life. Meditate to calm your mind its really helps. Everything is possible. Never give up.