Remove the flaps if they are installed, disconnect the ASF, remove the anti-spin devices on the wing tips and then have an experienced pilot fly it and trim it out for you. After that, you will have a perfectly good trainer plane to learn on.

I have a Nexstar and it did not fly correctly until we removed all of the "learning aids". I was not a beginner when I bought it but I had been out of the sport for a while. On the first flight, I had the same problem as you are having. After adjusting the elevator, the plane wanted to fly in a "crab" all of the time. The problem was the anti-spin devices on the wingtips. After removing these, it was a pleasure to fly.

As for the ASF, it may bring the airplane to straight and level flight with hands off, but only if it is adjusted properly. It works by sensing the angle of the sun. If the sun is too low in the sky as in early morning or evening, it will not work correctly. In the best case, it forces you to continue to hold control throws all the way through turns and such. Unless you intend to fly with it forever, I think that is a bad habit to learn. If you do that with the ASF disconnected, the plane will continue to roll over until it is inverted. Normally, you bank the plane into the desired angle and release pressure on the sticks until you have made the desired turn and then add pressure in the opposite direction until level flight is acheived.

The Nexstar is a fun airplane to learn with and to fly. As you get more comfortable, gradually adjust in more control throws and it will be quicker responding and more aerobatic.

Good Luck and Good Flying.