in some locations the game spam "Loading error" pausing the game i need help y load old save slots and every time i enter in the desert zones the error spawn and the error 
Sorry that you're having troubles... Obviously you tried the "perma-fix" and refresh method, so let me offer a different solution:
Just before entering the zoned area of troubles, spam the enter key until you get to the caves. You'll know what the caves are when ya see em.
Save the game once you're in the caves, and reload the game (closing the game may be a requirement). It fixes it on a "temporary" scale until the devs get it fixed.
i have a question I just had just completed the mission where you have to save your friends from the Decay spell and now there are no more Story missions listed does that mean that is it for this current version and if you would be so kind can you tell me where to find the fourth person for the party
All of Chapter 4 is new content, and thus are not part of the Quest lists. Chapter 4 is also the latest issue for this game, so new content will be announced when the Devs decide to drop another update. The dragon quest therefore is the last major quest that is available to players. (After the decay quest is the dragon quest).
Technically, there won't be a 4th person, though I would love for that to happen. You'll see other followers pop in and out, but they are temporary compared to your main three, thus they won't have the special ability that your main three will have.