Why do gaseous planets spin faster than telluric planets? I've seen thats because of primitive nebula but I didn't understand why? Could someone help me? I would appreciate a lot!
There isn't such a great difference between Earth and Mars (at about 25 hours) and the gas/ice giants (between 10 and 20 hours). Earth had a day of about 6 hours in the early Solar system, but has been slowed by lunar tides. Small planets will not accrete gas in their early formation, and so will not pick up angular momentum from accretion discs, which can explain why Jupiter and Saturn have rapid rotation rates.
Mercury and Venus are slowed by Solar tides. In the case of Mercury, it is in a resonance between its orbit and the solar tide. In the case of Venus, there are significant atmospheric tides, that slow it down (It actually spins backwards, and the full explanation is incomplete.)
So the answer is three-fold: Distant gas giants pick up lots of momentum in their formation, they are not much affected by Solar tides, and the differences between them and the rocky planets are not actually so great anyway.