Learn Italian: Il garage è pieno di scatole vecchie.

In Italian, the adjective pieno (full) is almost always followed by the preposition di to say what something is full of. It translates directly to 'full of' in English.

Why doesn't di combine with an article here, like delle scatole?

When a noun is used in a general, uncountable sense after pieno di, you just leave di by itself. If you were talking about specific boxes, like 'full of the old boxes we packed', you would combine di and le to make delle scatole.

Why does vecchie end in '-e'?

Adjectives must match the noun they describe in gender and number. Scatola (box) is a feminine word, and its plural is scatole. Therefore, the adjective vecchia (old) changes to its feminine plural form, vecchie, to match.

Why is garage masculine?

Foreign words borrowed into Italian usually default to the masculine gender, which is why it takes the article il. Even though it is spelled like the English word, Italians pronounce it the French way, ending with a soft 'zh' sound.