Hello,
I am afraid the Loco translate is the only way to translate the stings in this case. Hello,
When you create the translation file in the same language which you have set in Dashboard > Settings > General, you can replace a string and rewrite it this way. Please check and follow this: https://localise.biz/wordpress/plugin/manual
You can remove the plugin and translations will remain. Also, translations would remain after each theme update.
Best Regards