Yeah well the construction of the sentences is different because the French language has Latin origins whereas the English language has german origins. English is probably the simplest and less elaborated language in the world. No offense by that, a language doesn't have to be complicated to be good.
To me the most complicated thing with the English language is the accent. When English people talk it's like they are singing lol it's a beautiful language.
There are many areas that I think I understand till it comes time to use them - when we learn and understand we have plenty of examples to work with, in the isolated incident there are no guide posts. In particular I find this when trying to differentiate the meaning of an adjective before and after a noun: eg la reine ancienne, l'ancienne reine.
But most difficult for me are the idioms - for instance the so many different ways to use faire, where just the difference of a prepostion in a structure can change the whole meaning. Probably this means I too am confused by the use of prepositions - which one to use where to mean what :(
Your point about the positioning of adjectives, is an area I'm researching at the moment - it confuses me also !!
My findings so far are;
Some adjectives can only go after the noun, whilst some can only go before.
Some adjectives can be used before or after the noun, changing the meaning completely (as you point out).
Putting one of these adjectives before the noun gives it a figurative meaning; putting it after gives it a literal meaning.
In your examples; la reine ancienne = the old queen, l'ancienne reine = the ex-/former queen.
This helped me somewhat, I hope it helps you.
If you find any good tips on this subject, I would be glad to hear.