Hi Mario,
If you want the front-end texts simply changed to your language, then each text can be changed on the back-end, for example:
– to change the placeholder text, you can do it here: https://i.imgur.com/UIS0mCa.png
There are no .mo and .po language files for these, because those does not support dynamic text variations. Once these fields change, the .mo and .po locale files are not usable.
If you have a multi-language environment, you can also translate these dynamic texts using either WPML or Polylang.