I tried activated the option to partition a disk, instead all my drive data disappeared in a few seconds I read online that there was a command line to activate the partition option on Disk Utility:

diskutil partitionDisk disk4 1 GPT HFS+ newdisk


Which is just supposed to unlock the possibility to partition THEN chose the partition size or erase. Instead it renamed the disk but it also made all my data disappear!!

Please tell me there's a way to retrieve it or I'm going to smash the Mac to pieces...
diskutil partitionDisk command does exactly what you described happening.  Partitions a disk, removing all volumes.  All volumes on the disk you ran the command on are destroyed.  So you partitioned disk4 and renamed it newdisk using GPT HFS+.  I'm not sure where you got the command information from but the command you entered did exactly what it was supposed to do.  I would recommend looking into data recovery services if you need anything that was on that drive.