Managing the population and expansion

Newbie here and just started playing 3 days ago. My current playthrough is night30 on easy mode and im lacking manpower to create walls of ballista for defense.

I have tons of food hut and couple of farms inside the walls but its not enough for the population to grow. And i ran out of fisheries.

Do i need to expand to more land and find anothet chokepoint to hold, or am i doing something wrong?

To compensate for this, i sold some towers from previously defended position to have enough manpower to build more ballista towers