French language Q&A Forum

Is there a lesson which covers this case of using an adverb "bien" instead of an adjective "bonne" ?  

J'ai besoin de supplementaire information sur l'usage de "en tant que". Remercie de votre assistance.

Why is there a "DE" here? Is the expression "fait de qch"?

Is the hyphen with 41 correct here? On the page Expressing numbers 70 to 999 in French it says no hyphen for 41?

Can one also say 'dont les Celtes' in this situation?

I had not come across this verb before, and thought it would behave like an ir verb wth a past participle of acquéri. Could you tell me which other verbs follow the same pattern  as acquérir? Or is it completely irregular?

I was doing the exercise (https://kwiziq.learnfrenchwithalexa.com/my-languages/french/exercises/judge/1833/14548249?response=4150265&page=7) to answer a question and now have one of my own:

There's the phrase: visiter les ruines du vieux château.

How come the rule that the definite article is omitted if there's an adjective intervening between de and the noun is not applicable here? I would have thought this should be ...de vieux château.