The problem of Pharaoh and Cleopatra

Buildings larger than or equal to three times three are at risk of collapse. Shortcut key d or select in the upper right corner, water supply w, fire protection f and so on.

The second question is too vague. Let's be specific.

First, you need a fortress, which is divided into Gong Bing, infantry and cavalry (only later). Then, Gong Bing can directly recruit unarmed soldiers. Infantry and cavalry need weapons and chariots respectively. Weapons come from weapons stores and need copper, and chariots come from chariot factories and need wood. Building a military school can give recruits more experience. Navy ships come from shipyards and need wood. Finally, when crossing the river, the army must be carried by a transport ship.

Usually, the army can only defend your city, and you will only be asked to send troops when Pharaoh or friendly cities need military support to defend or attack. You can't send troops to other areas at ordinary times.