I just recently signed the lease ( June ) I moved in in the middle of a month . The landlord gave me a verbal agreenment that he will fixed the window by putting in a biger one so I can install AC. Its July now the window still remains unfixed and since it's a attic room the temperature in the room is unbarable ! The terms of breaking the lease is 2 months notice and find someone for replacement. The 3 other girls who lived there do not want to cooperate and help find a new roommate which should be in their interest since they are the one who are going to live with the new roommate . Any shouggestion of what should I do ?

Get a smaller A/C or a portable unit.

I don't want a portable AC . I want to have a normal window . Plus portable AC is too expensive. The landlord clearly said he is going to replace it ! Other suggestions ? Can I break the lease because of that ?

Not unless it is in writing as part of the lease agreement,

And to be honest you can wait and be hot, or get a different air unit, you may call the landlord and ask him if he is going to pay you the difference in cost of the air unit. They make models that vent out a window though a hose.

Or ask him what handiman he uses and you will call him to get him over and let him bill the landlord