Please someone can tell me how to go to the east mines after finding and using the lever? I can't find the dragon ore and I can't get any kind of ores from the ground. I think there is some kind of mechanism to change the way of the trolley but I didn't arrive to solve this mechanism ( or combination ).... Please be quick or I'll become crazy.......

When you find the lever for the east trolley - you have to USE it on the trolley to fix it.
Down the west trolley, if you explore completely, you will find a switch (you can see the track through a window) - there is a similar switch down the east side as well. Changing these switches will change where you go on the east trolley. If I recall correctly - not switching the one on the west side and using the east trolley took me right to the area (with lava) where you can find dragon ore.
Also look through the threads for one by Xignal - he's got some great maps and walkthrus for the various areas which might be a big help to you.
Wyv

Look around for pick axes and use them on the ore piles.