Avoir is one of the two most important French verbs and has irregular conjugations in just about every tense and mood. Avoir literally means "to have" but also serves an an auxiliary verb and is found in many idiomatic expressions.
What do buying clothes, talking about art, and shopping for fruits and vegetables have in common? Color! If you want to make sure to buy red tomatoes and critique an artist's use of green, you'll need to know the French colors.
Contractions occur when two words are combined into one, sometimes with a distinctly different spelling. In English, contractions like "won't" are optional and indicate informality. In French, however, contractions are required, regardless of the register you're speaking or writing in.
The preposition dans usually means "in," but as always there are exceptions. Dans can't be followed directly by a noun - it's always followed by some kind of determiner, such as an article or possessive adjective.