Install libqscintilla2-qt4-l10n by entering the following commands in the terminal:
sudo apt update sudo apt install libqscintilla2-qt4-l10n
Scintilla source code editing widget for Qt4, translation files
QScintilla is a text editor for Qt4 with features especially useful when writing and debugging source code. These include support for syntax styling, error indicators, code completion, call tips and margins. . This package contains translations for libqscintilla2.