Come against usually has the sense of “attack.” See verse 3.

From every quarter is a difficult construction, but Hebrew Old Testament Text Project proposes the meaning “from every part.” We could then translate the first line as “Attack it from every side” (Good News Translation).

Granaries are “the places where its grain is stored” (Good News Translation). Her in the construction pile her up like heaps of grain is best taken collectively as the “loot” (Good News Translation) taken from the city. In the other two places where her occurs in this verse, we may substitute “the nation.”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on Jeremiah. (UBS Helps for Translators). New York: UBS, 2003. For this and other handbooks for translators see here .