It's a very good start and, at your age, it is important to acquire the art of objectively learning from criticism without taking any of it to heart. Improvisation at its finest is a profoundly spontaneous expression of our most precious musical impulses. It is not for nothing that the greatest creative minds in piano history have, virtually without exception, prized it above most other functions. During its best moments there comes an ecstatic inevitability wherein one feels, as it were, a channel for an infinite succession of transporting ideas. The conscious and unconscious come into perfect balance in a sort of feedback loop, producing a transporting state almost impossible to describe in words.
There are many other ways of doing it, such as the "mental arithmetic pattern" way, and the "bag of tricks" way. While their development is very clever, by no means to be despised, and many professionals use no other ways, they cannot, in their nature, touch the deeper responses because they exist only at the conscious level. A bag of tricks is just a bag of tricks no matter how big it is.
Therefore I concur with the essence of the previous comments but I would not have couched it in such harsh terms. Discouragement does nobody any good, especially a young person. Improvisation is bigger than a lifetime and you are young with plenty of time and obvious talent. In addition to the excellent advice of Derek, I would tend to try removing speed and virtuosity altogether; let the improvisations stand on music alone for a while. A good way to do this is to improvise musically compelling slow movements.
It also has to be said that your best improvisation will be when you are yourself, not Cziffra, not Jarrett, not even Liszt or Bach - yourself. Finding exactly what "yourself" is, and bringing it out, is an immensely satisfying, life-long activity. It can also never do any harm to find a teacher who improvises; I know they are rare but they do exist.
Topic: VIDEO!my improv (tried to do it with style) you like it? please watch!