Finding the area of an irregular polygon with more that three sides is not as easy as it might seem. The problem arises from the fact that the lengths of the sides does not determine the shape. Even in the situation where all sides are of the same length the polygon might have quite different shapes and quite different areas.
In your situation, with different length sides the situation is even more complicated.
To determine the area of your lot I need enough information to determine its shape. The size of one of the angles will suffice or the length of a diagonal, but without this information I can't offer any help.