If a creature with trample attacks me and I block with a creature on which damages are prevented, will I receive extra damage over my creature toughness?
Yes, the attacking player only has to assign enough damage to the blocking creature for the attack to be lethal, that means damage equal to all the blocking creature's toughness, whether the creatures actually die from combat damage is not strictly necessary. There may be a myriad of ways in which damage may be prevented, but that does not change how the damage is assigned.
702.19b. The controller of an attacking creature with trample first assigns damage to the creature(s) blocking it. Once all those blocking creatures are assigned lethal damage, any remaining damage is assigned as its controller chooses among those blocking creatures and the player or planeswalker the creature is attacking. When checking for assigned lethal damage, take into account damage already marked on the creature and damage from other creatures that's being assigned during the same combat damage step, but not any abilities or effects that might change the amount of damage that's actually dealt. The attacking creature's controller need not assign lethal damage to all those blocking creatures but in that case can't assign any damage to the player or planeswalker it's attacking.