Is it normal that after installing (and using for a hour) the nzxt cam my gigabyte geforce gtx 960 4gb videocard is overclocked to 1388 MHz when i didn't touch either the nzxt software or the oc guru II (in the oc guru it should be limited to 1279 MHz) and i do not know if my card is in danger so please someone help!
It's normal if it's reading the actual boost speed vs. the advertised speed from the manufacturer. Nvidia will list a base/boost clock w/ their cards for reference. However, the actual boost can be considerably higher if the temps/voltage are kept in check. My 970s are rated for an 1178 boost clock, but If I use GPU-Z to record a logfile from in-game, they're go to 1242 on their own. You should be fine.
It is called the magic of a smart GPU... IUf it is running at its designated speed, and is well below its max temp, it stops for 1 millionth of a second, smiles, laughs, and still within that one millionth of a second, it kicks up the speed some. And it keeps doing that until the twemp is below, but very close to its max temp.
All of the Nvidia GPU's do this today. And they will drop speed just as fast, but with a frown on their faces, if the temp ever goes above the max temp.