We reported to the developers of kdenlive the lack of translations in the latest appimage and a few hours later the Kdenlive Development Team remedied. Unparalleled efficiency and friendliness, professional and efficient as the software they produce. Congratulations!
Download kdenlive kdenlive-19.04.3b from this link
Open a terminal and type the following commands
mv kdenlive-19.04.3b-x86_64.appimage kdenlive.AppImage
sudo rm /opt/App/kdenlive.AppImage
mv kdenlive.AppImage /opt/App
chmod 777 kdenlive.AppImage