When people talk about tenements, they are usually referring to old, dirty, and dangerous buildings. These buildings were usually built near the edge of a city, so they could get a lot of people in close proximity.
A bricklayer is someone who is skilled at laying bricks. They need a lot of strength and stamina to work on a bricklaying project.
The middle age is the stage of life between the young age and old age. It's a time when people are in the middle of their careers, and they are starting to become more responsible.
An octogenarian is a person who is old enough to have a retirement plan, but who is still alive and kicking. Octogenarians are usually very healthy, and they are often very active.
To bicker is to argue or to fuss with each other. When you bicker, you are usually arguing about small details.
When people are working together, they are usually called workmates. Workmates can be friends or co-workers, but they are usually working together to achieve a common goal.