I can confirm this, but only if you apply the new theme "CDL" theme in the Style Editor. If you switch back to the old theme "Light", the translation is correct.
Sorry this did't help. I already found out that other German customers have the same problem.
ive Upgraded our Testenvironment to 2018.3.1 and the translation problem is solved. If you have further questions, call me in Koblenz.