So there was Roman province of Germania
Whose name was deliberately chosen to obfuscate the fact that the vast majority of Germania was in fact not conquered and remained unconquered as long as the Roman Empire existed. There was some trade with German tribes east of the Rhine, but as Tacitus noted, the Germanic people remained untouched by the Roman ways for good and ill.
Constant genocide and slave hunt on native Sarmatians (Serbians) continued behind borders of the province
Untrue, there were some Roman excursions into Germania, however sometimes centuries passed between them.
was conquered but Romans were unable to diges
Completely untrue. The province of Illyria - which todays' Serbia is a part of - was one of the most wholly Romanized provinces of the Empire. Evidence for this is the number of Senators and Emperors it produced and the lack of any uprisings against the Roman rule after the initial revolt was crushed.
Roman name of Germania became name of new nation- German nation
Actually it did not. The English language is the only language that borrows from the Roman name. In Germany it is called Deutschland, (which has no Roman origin) and the other countries often used the name of German tribes they interacted with as a name for Germany.