Now that scientists found the primordial gravitational waves that formed shortly after the big bang,and we all now that just after the bang the 4 fundamental forces were unified can we consider that these waves are the strings that we're looking for,that unify again these forces?
First of all, we still do not know if the 4 fundamentals forces can be unified. The best we have came up to are grand unification theories (GUT), which join three of the fundamental forces except gravity. The fact that gravitational waves have been detected, may point towards GUT since they address energies of the GUT scale.
Nonetheless, assuming that String theory, which is a good candidate to unify gravity with the other forces, is correct, there is a theory based on them which is favored with the BICEP2-Data. This is a theory developed by Robert Brandenberger, called String Gas Cosmology (see http://arxiv.org/abs/1105.3247). This theory suggest that the universe started with a gas of strings whose thermodynamic properties avoid the temperature singularity of the big bang. This theory also predicts why we see 3 dimensions of space and one of time. If two strings meet, their edges can form a single, twisted loop. That would release three dimensions of space and one of time, which can then swell to the scales we see in the universe today.
Furthermore, the BICEP2 data suggest a blue tilt in the gravitational waves predicted by string gas cosmology and hard to explain by standard inflationary cosmology, which predicts a red tilt. So if the BICEP2 data is confirmed and this blue tilt is favored, then it would be a evidence for string theory and oponents cannot say that string theory does not match with data.
So if your question is if the BICEP2 data can help prove string theory, you are answer is yes
Nope, gravitational waves were predicted by Einstein's General Relativity theory which is a very successful theory of gravity. We still though do not have a working theory of Quantum Gravity and cannot therefore unify these forces as of yet.