God says this to the army that will attack Jerusalem. The word "her" refers to Jerusalem; cities were often spoken of as if they were women. Alternate translation: "Cut down the trees outside of Jerusalem" (See: [[rc://en/ta/man/jit/figs-personification]])
Siege works are either high mounds of dirt or high ramps made of wood that the enemies build outside the city wall in order go on top of the wall and attack the people inside the city.
Here "it is filled with oppression" represents people there always oppressing people. Alternate translation: "because its people are always oppressing each other" (See: [[rc://en/ta/man/jit/figs-metaphor]])