Hi sir, I have been smoking for 7 years and my age is 27. I can't able to stop smoking. What is the possibilities for me to get cancer and what are all the symptoms...

You are smoking, so you have a far higher possibility of getting cancer. You can Google what all the symptoms of the various cancers that are smoking related.

Also suggest Google to find images of mouth, throat, lip esophageal and lung cancer. (and those aren't the only kinds smoking related) and the more you smoke the greater the chances. And even if you dodge the bullet on cancer... there is emphysema, Imagine slowly suffocating to death even with a oxygen tank over a period of years with it getting progressively worse all the time ... which is basically what happens with it.

Maybe looking at those will help give you the willpower you need to stop.