Something that is lost and then found is recovered.
The word is "classifieds" (classified ads).
There is no one-word substitute in English for "son-in-law."
The word you want is florist.
Sportsmanship is a word substitute for spirit of game
The analogy of lost is to found as autumn is to spring. Both pairs involve a transition from one state to another - from being lost to being found, and from one season to another.
The word metalworking is one word.
eat, use
One possible substitute for "their" is "his" or "her" depending on the gender of the person/people being referred to. Another substitute can be "its" when referring to a non-human object or entity.
The word that works is idiot.
Elevate
Traditionalist
Omnipresent