All languages work, but polish gives me broken characters (see attachment).
They original text is stored as *.rst file (in German) and then I translate them into *.po files.
# SOME DESCRIPTIVE TITLE.
# Copyright (C) Beat Gurtner
# This file is distributed under the same license as the Dokumentation des
# Sakkadentrainers package.
# FIRST AUTHOR <EMAIL@ADDRESS>, 2019.
#
msgid ""
msgstr ""
"Project-Id-Version: Dokumentation des Sakkadentrainers\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2018-07-26 14:43+0200\n"
"PO-Revision-Date: 2019-12-29 17:38+0000\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=utf-8\n"
"X-Poedit-SourceCharset: UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Generated-By: Babel 2.4.0\n"
"Last-Translator: \n"
"Language-Team: \n"
"Language: pl\n"
"X-Generator: Poedit 2.2.4\n"
#: ../../index.rst:7
msgid "Willkommen zur Dokumentation des Sakkadentrainers"
msgstr "Witamy w dokumentacji Sakkadycznytrener"
#: ../../index.rst:9
#: ../../index.rst:11
msgid "Inhalt:"
msgstr "Treść:"