I am having calibration problem i touch the uper part of screan but the down part highlites can not use my go 520, tried to make calib.txt file and cal.txt file but nothing changes can someone help me

If done correctly it will change, depending on the NC version there are come values changed in the file and it called cal.txt or cailb.txt - do a Google search for it and you should find two or three tuts that explain it in detail.
Always start with the values displayed at your system boot screen adn work your way through only changing one valu at the time - be aware that you have to pay attention which is for X and which for Y !!

It might be easier and fast to order a replacement touchpanel off Ebay for a few bucks.