Alors je te me en gras ce que j'ai changé et je laisse entre parenthèse ce que tu avais mis! ^^ J'ai aussi supprimé les accents que tu avait mis sur le "é" de Cedric! Je sais c'est bizarre mais en anglais y'a jamais d'accent! C'est quand même bien, je t'ai surtout corrigé des fautes d'expressions!

It was in the night. The weather was stormy and there were a lot of claps of thunder. Suddenly there is a shout. Cedric gone (was going) to the room of his parents and he asked them if he could (must to) sleep with them. Cedric's Frather (The father of Cedric) accepted, so (and) Cedric went between his father and his mother. There was again a shout. Then Cedric's grandfather (the grandfather of Cedric) arrived in the room. He wanted to say something but Cedric's father (the father of Cédric) didn’t let him speak because he thought that the grandfather wanted to sleep with them too. He shouted so (and) the grandfather went out of the room.
The next day, when the parents of Cedric woke up, there was a lot of water in their living room.
That was what the grandfather wanted to say!