i got a few of my files removed by DMCA notice from my FF account.
What do i do ? will they sue me ? am I in d@@p sh!t ?
You've not actually had anything filed against you personally though?
The take-downs are usually to the providers (FF in this case), with them having to take down the copyright material from their service ASAP so that they can't get into trouble for hosting it. It protects the providers from the actions of their users (and isn't really used for punishing the user themselves).
Normally the provider wouldn't be allowed to give any of the end-user's personal details to the copyright owner, unless the copyright owner had also got a court order or warrant to obtain them, but that would be a separate thing to the DMCA take-down request. So chances are it won't go any further than being between the copyright older and FF.
But it does mean that someone has been looking at your files on FF, so like ravdev says it may be an idea to change to another provider (with a different username) and not put anything else on FF.