What is "Hatikenu"?
Rashi #1: It is based on "Tik" (case). We will take them (cause them to come) out from the city.
Rashi #2: It is uprooted, like "Hatikem k'Tzon l'Tivchah" (Yirmeyah 12:3). Radak
Why is "v'Nasnu Lifneihem" repeated from verse 5? Also, this verse already said "they will say 'they are fleeing from in front of us'"!
Malbim #1: "V'Nasnu Lifneihem" corresponds to "Hatikenu Osam Min ha'Ir." "Ki Yomru Nasim Lefaneinu" corresponds to "v'Yatz'u Achareinu."
Malbim #2: We will continue to flee after they are uprooted from the city, until we uproot them to the Midbar, so the ambush will have time to set the city on fire and close the south side in front of them, like will be explained.