If you want or need custom translations different from the translations provided by the Community you can do that easily:
Create your translation with Poedit (a app for your computer, https://poedit.net/wordpress) or Loco Translate plugin (inside WordPress, https://wordpress.org/plugins/loco-translate/) and upload the translation file there, to this path inside your WordPress installation:
for example the German version would looke like that:
/wp-content/languages/ is the global translation folder – if it does not exist yet in your installation just create it.
Note: The exact same steps need to be used for a custom wording in WordPress’ default English, which is
en_US – then the
.mo file is named