Ho my god it is then true you guys are awesome!
I thank you klaus 1 And I thank you Terence Delvin.
Although I am leaving in Germany and I am French speaker I decided for convenient purpose to use english for my MBP. I am using the version 10.13.3.
Now I am at peace.
I must say what brought me on the edge.for two weeks ago I went to an It shop in Berlin. Because my casing got a bump that drove me mad, and wanted it to get fixed. By the way they did a nice job. Although I locked the EFI and encrypted my drive. I noticed that "library/preferences/systemconfiguration" was created and modified a day before I got my computer back. Hence I ask the owner who assure me he did not use it. That's where I got suspicious.