how can set the sensitiviti on my hobbico nextstar it is just to sensitive.
iam using a futaba skysport6 radio with s3003 futaba servos

Try reducing your control surface throws. Move the linkage IN on the servo arms and OUT on the control horns that are on the control surfaces.

With reduced throws, the plane will not be as sensitive. As you gain experience, you can start moving the throws so you have more movement on the control surfaces.

You can also set in some exponential with your radio (if it's an option--I'm not familiar with that radio...)

2slow, I don't think he is able to do exponential 6 channel non computer. I agree just move them in on the control horns and your good. When you progress and outgrow that radio, the computer ones and make it where you flip a switch to change rates. I just got mine and i have 3 different rates set up for elevator rudder and ailerons by the flip of switch

Everthing above sounds good.
Check if your center of gravity is to far back. That will make it sensitive or even unflyable.
Even if its right on you might want to move it to the front of Hobbico's suggested range....they track better nose heavy.

A little note: They track better nose heavy and they must land a bit faster too.

mblue2050 is right about the CG. Remember to check with the tank empty.