I'been playing for a long time but when i have to improvise, and put all the things that you learn like scales, arpegios, pickin technique etc, it seems lke i forgot everthing! and the scales... looks like i never study them before...lack of memory? wrong study method? help me ! thanxs....
Does "when I have to improvise" mean when you're somewhere where there might be some public pressure affecting you? If so then it's quite normal.

Well, to become good at improvising is like getting good at so many other things: you need to practice. Once you learn something new (like some scale, arpeggio, other stuff you mentioned) you try to sneak it into your "vocabulary" by getting a backing track (if you can) or some kind of click/drum going and just using that thing in many different ways to fit the content of the backing track (again, if one's available). After a while you'll be able to use this "vocabulary" while improvising more efficiently.

Also, do check out this lesson by Marty Friedman, it has good advice and everything concerning improvising: