O Oh-if it's a neutral building, it can't be maintained. Only the building built by oneself can be maintained;

There is a team logo at the bottom of the map. Click the left button, and then the mouse becomes a team. Move the team to the building to be repaired, click the button on the left to start the repair. Need a certain amount of money, right click to cancel. If multiple buildings need to be repaired, just follow the same steps as above, instead of "right-clicking to cancel".

Engineers can build, let engineers into the building to be repaired, and build several.