The thing is Jarmenia, that you probably haven't got the line down.
Everyone here is rambling on about setup changes etc., things that could definitely gain you some time, yes, but it isn't necessarily what's going to make you a better driver.
You say you have the line, but first of all, ask yourself if you have the timing? Are you braking as late as possible? Are you minimizing your free roll? Are you getting on the throttle as fast as possible and as much as possible after every single corner?
Are you getting the best out of yourself?
This very question is primary. Every thing else comes second. You need to be pushing yourself to the absolute limit to be pushing the setup to the absolute limit. If you're not doing that, small setup changes are going to do very little for you.
Obviously the paradox here is that you are never getting the best out of yourself - there's always room to push more, concentrate harder. But the key point here is that you are probably not pushing yourself hard enough just yet to be worrying about setups.
Training is the key to getting better of course, but I have a few links that might help you:
http://www.virtualracersedge.com/driving_tips.htm
A series of driving tips.
http://www.virtualracersedge.com/physics_of_racing.htm
"The Physics of Racing" is a very famous series of articles from a software engineer and sparetime racer. It's very heavy on math, but the first couple of chapters are still essential to any driver.
These two links are here to help you with the same thing. You might know how to drive the car, but do you know why that is correct, or maybe why it is incorrect? These links are going to tell you this.
And finally when you want to start making your own setups and setup tweaks, here is one guide to get you started:
http://www3.sympatico.ca/cbarnett/SetupMatrix.html
Hope this is of help to you and other people here.