I am trying to rotate the curve but I'm unable to get real results. It goes very high to very bright values or very low. What I am doing wrong? I'm not able to get the curve to an even point and real exposure.

This might happen if the exposure for your images covered a large range, you used adjustments that were too large or you did the adjustments too close to each other.
Hard to say, because you didn't include a screenshot.
It's important that you do constant, frequent and small adjustments and keep the brightness in a rather small range. Easiest the shooting is done with qDslrDashboard, as I explained in my tutorial: https://lrtimelapse.com/gear/dslrdashboard/

for that sequence just try to do bring the orange curve as close to the horizontal center as you can, then do the rest via Exposure on the regular keyframes. You might also post a screenshot here, then I can tell you in detail what's going on.

Thanks for the answer! I am always having trouble to know what's the correct time to do changes to my exposure :-(

Here's a screenshot

Those adjustments look way too large. You should adjust in 1/3 stops only. Can you send me that sequence via WeTransfer or https://fromsmash.com/ ?
Send it to support(at)lrtimelapse(dot)com.