I solved the problem !
It could has been solved yesterday but I did not realised that the situation as occured to me is the freezing caused by graphics. Thanks to NGIB who noticed this fact I have found how to proceed.
All guidanance is clearly stated here:
Solving freezes with NVIDIA GeForce GPUs - http://www.linuxmint.com/rel_rosa_mate.php
I followed step by step these instructions and everything went smoothly. finally
To all of you - take care yourself and have a nice time. Bless you.