Hi there robertosogni, I hope you are doing well?
I have found thsi which may help prepare you for the next limits up, but I'm obviously not sure of your present ability level, although you seem to be doing very well!
These were extremely popular when the were released and I think most of the content will be just as relevant today. The second links to an especially commended series.
#1
http://www.pokerstrategy.com/video/#searchtext=Major%20Leaks%20on%20NL50%20SH&key=tag
#2
http://www.pokerstrategy.com/video/#searchtext=crushing%20nl50&key=all&contenttype=0&gametype=0&tablesize=0&languages=en&levels=basic,bronze,silver,gold,platinum,diamond&lowerlimit=0&upperlimit=100&ob=date&od=desc&page=1&rpp=10
Most likely others can help further, but I hope this helped somewhat.
Enjoy the videos, have fun moving up and above all run good! ♠_cool:
Mal.