90% of all problems using using Keylight come down to improper technique and failure to do some studying on the effect. I would suggest that you type Keylight in the search help field at the top right corner of After Effects and check out the community resources and help files. You can use masks as garbage mattes and you can adjust he matte to make almost every green screen shot work well. If you can't pull a good key then either your footage is very poorly shot and highly compressed or you are not adjusting the right controls.
Without a screenshot of your project and the footage you are working with it's impossible for anyone to give you the settings that will work. To diagnose your problem start by selecting the layers that are giving you problems and then press the U key twice to reveal all modified properties. Unless the shot is perfectly shot you should see at least 7 or 8 modified properties for Keylight. If you are only seeing 3 or four then you need to do some studying and figure out how to correct your matte.
If you still can't get it to work then take a full screen screenshot and drag it to the reply field on this forum or use Print Screen and just paste making sure you have selected the problem layer revealed the modified properties.
instead of using crop square , i want freedom to select the part that i want instead of limited to square
That's what garbage mattes are for, but yes, as Rick said, you seriously have to read the help. No point in flying blind and make yourself look stupid on a forum...