Plasma long range em interaction I've seen that charged particles in plasma are shielded at a distance of a Debye length, so how is it possible that charges in plasma interact on a long range distance too? It seems impossible to me because they should not see each other when they are far.
Maybe an example would help
 A: 
I've seen that charged particles in plasma are shielded at a distance of a Debye length, so how is it possible that charges in plasma interact on a long range distance too?

Long-range is referring to the Coulomb interaction between free-charged particles within a Debye sphere.  A Debye sphere may seem small to you, but compared to atomic interactions or neutral-neutral interactions, the distances can be huge.

How it's possible that collectivity behaviors happen?

The collective behavior of a plasma results from the accumulated effects of all these Coulomb potentials.  Electric fields do work to get rid of themselves, thus how Debye spheres form.  Because of the long-range interactions of the electric fields, you cannot "push" one particle without it affecting all the others within a given Debye sphere.  Thus, the system begins to behave somewhat like a fluid.
Note that most plasmas, by volume, in the universe are in the range of weakly collisional to collisionless.

if all the particles are shielded they should be independent after a certain distance right?

Yes, they are over distances longer than roughly one Debye length.  That does not impede collective behavior.  Take the water in a glass of water, for example.  Any given particle's immediate sphere of influence is defined by its collisional mean free path.  In this case we are talking about length scales on the order of sub-microns (it's actually much much smaller than a micron).  Unlike a plasma the molecules in water do not care about the collective influence of a surrounding sphere of water molecules, they only care about the next water molecule with which they collide.
Note that when the collide, they don't actually touch.  Neutral particle collisions are also mediated by the electric fields from Coulomb potentials but they don't see these fields until the inter-nuclei separation is on the same order of magnitude as the collisional cross-section of interaction.  For water-water molecule collisions, the cross-section is on the order of ~10-15 cm2.
In fact, if you are worried about shielding, you can actually think of a monatomic atom as a super simple analogy to a plasma.  The nucleus is positively charged while the electron cloud is negatively charged.  However, outside the electron cloud, the total electric field from the atom asymptotes to zero rather quickly.
