is string is the lowest and smallest element in the world?can it solve the wave and particle problem?

Answer 1

String theory is just a theory. It was made up to try to explain physical phenomena. Scientists are still trying to prove or disprove it.

The infamous Einstein theory of relativity, is still that: a theory. It did not explain everything in the universe, either.

Answer 2

"String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that are the basis of the Standard Model of particle physics. String theorists are attempting to adjust the Standard Model by removing the assumption in quantum mechanics that particles are point-like. By removing this assumption and replacing the point-like particles with strings, it is hoped that string theory will develop into a sensible quantum theory of gravity. Moreover, string theory appears to be able to "unify" the known natural forces (gravitational, electromagnetic, weak and strong) by describing them with the same set of equations.

No experimental verification or falsification of the theory has yet been possible, thus leading many experts to turn to the alternate model, Loop quantum gravity. However, with the construction of the Large Hadron Collider near Geneva, Switzerland scientists may produce relevant data.

Studies of string theory have revealed that it predicts not just strings, but also higher-dimensional objects (branes). String theory strongly suggests the existence of ten or eleven (in M-theory) spacetime dimensions, as opposed to the relativistic four (three spatial and one time)"

This, and more, available on the free, online encyclopedia, Wikipedia at:
http://en.wikipedia.org/wiki/String_theory

Hope this helps!