If you try to change the payment terms in 'Setup - Dictionary Setup - Payment terms' you get the french text instead of the actual text in the choosen language.
It doesn't matter if you try that with an english or german GUI. The payment text you want to change will always appear in French. You have to copy&paste your original text first, if you don't want to write it from scratch.

Because French is stronger than DataBases !

You made my day!
But I think, this is wishful thinking

On installation, the DB is populated with French texts. They get translated by the translation files on rendering the page, but the translation is not called on changing the fields to editable text inputs.

This can theoretically be solved by choosing the base language before populating the database. Keep in mind that you'll have to edit the translations as well if you have to support multiple languages.