My dream last night

My dream last night was very strange.

I was in an old train with many people. I think there was my mother and my cousin were there, but I don't remember well. The train was sounding sounded terribly terrible. It seemed like the train would was going to brake break.

Suddenly, the train started going much faster more fastly as much as and I was afraid of that. It seemed like a rollercoaster. A wagon of the train broke and it fell into the abyss. I was so afraid and my wagon fell to off a precipice.

Mysteriously, all the people were alive and happy. I don't think know what my dream meant. I am confused.

My dream last night

My dream last night was very strange.

I was in a old tren train with many people. I think there was my mother and my cousin, but I don't remember well. The train was sounding terribly and it It seemed the train would brake. (Although not wrong, sometimes it is better to join two small sentences to make things flow easier.) 

Suddenly, the train started going more fastly faster which made me afraid.  as much as I was afraid of that. It seemed like a rollercoaster. A wagon of the train broke and it fell into the abyss <--nice word). I was so afraid and my wagon broke into pieces.fell to a precipice. (I think you might be trying to say "broke into pieces"?)

Mysteriously, everyone survived and all people were alive and happy. I am not sure don't think what my dream meant, I am confused.

Using the word wagon in reference to a "train" is not entirely wrong.  The "wagons" of a train are commonly called, rail cars, or box cars, and if it were a passenger train, the last car at the back of the train would be called the "caboose".  I'm glad everyone was ok, that was a scary dream indeed! :)

My dream last night

My dream last night was very strange.

I was in a old train with many people. I think there was my mother and my cousin were in it too, but I don't remember clearlywell. The train was sounding sounded/creaked terribly. It seemed that it was  the train would braking.

Suddenly, the train started speeding up so fast that going more fastly as much as I was became afraid of that. It seemed it had become a rollercoaster. A wagon of the One train car broke away and it fell into the abyss. I was so afraid and my wagon scared that mine was going to fall into a precipice.

Mysteriously, all the people in the fallen car were alive and glad happy. I don't think what my dream may mean but I am confused.

My dream last night

My dream last night was very strange.

I was in an old tren train with many people. I think there was my mother and my cousin were there, but I don't remember well. The train was sounding terribly sounded terrible. It seemed that/like the train would brake break.

Suddenly, the train started going more fastly faster, as much as I was afraid of that ("as much as that scared me" would be more natural). It seemed (or felt) like a rollercoaster. A wagon of from the train broke off, and it fell into the an abyss. I was so afraid. (Then?), my wagon fell to a from/off of a precipice.

Mysteriously, all people were everyone was/all of the people were (still) alive and happy. I don't think know what my dream means, and I am confused.

*Mainly just a couple of style things to work on. Nice job!