What is the meaning of "v'Hisi'o"?
Radak: They will lift [ropes to the city to carry it to the valley. This is an exaggeration.]
Radak citing Targum Yonasan: They will gather.
What are "Chavalim"?
Rashi citing Targum Yonasan: They are camps. This is like "Chevel Nevi'im" (Shmuel I 10:5), "Chevlei Resha'im" (Tehilim 119:61). Radak - perhaps Yonason refers to ropes of the tents in the camp.
Radak: Ropes.
What will they take to the valley?
Rashi: The wall of the city.
Radak: The city. This is an exaggeration. Even though ha'Ir is feminine, it says Oso (masculine), i.e. the strong tower in the city. I.e. even if there will be a strong tower in the city in which everyone will gather, we will carry the city and the tower to the valley.