Translation:Do not put the new wine in the old bottles!
It's reffering to Mark 2:22. You'd have to read even before the verse.
Jesus came to the earth to bring in a whole new order, where the grace of God, operating through faith, would be the main motivating principle, instead of the obedience of the Law, given my Moses, motivated by fear of punishment. Jesus' enemies could not understand this, so they criticized Him and His disciples for not doing things the old and accepted way of the Law. The new bottles foreshadows the New Covenant; and the new wine forshadows the gift of the Holy Spirit, which was to fill those who believed in him, after he died for our sins and rose again from the dead. Therefore, this phrase said by Jesus, "Do not put new wine into old bottles, or else the new wine will burst the bottles, and the wine is spilled, and the bottles will be ruined," meaning the Gospel that will only fill with rage and fury to those under the Old Testament (Pact), and will despise it and let it go.
So it's more than just an idiom, but a spiritual teaching. :)
We generally prefer to put adjectives after nouns. When they are before they make the sentence sound poetic, so put them after the noun and you'll be 90% right. There are some exceptions but I think it's more about the construction than the adjective itself. For example, when possessives are used, the adjective will come before the noun. Sometimes the position of the adjective will change its meaning, as in "amico vecchio" vs "vecchio amico": they both mean "old friend", but the first one is old for his age while the second has been friends with you for a long time.