Hi,
If you still have the falang_content table in the database, you will still see the translations from there in your backend, even with Falang disabled.
However, if the Falang driver plugin is disabled, the translations won't be used on the frontend.
If you want to switch to the built in translation system, you need to rename the falang_content table in the database. That way, you'll loose the translations in your backend, and you'll be able to add them back with the built in translation system and they will then appear on your frontend.