How do i calculate the perimeter and the area

It is a semicircle so you'd use this formula for the area:

πr² / 2

Then substitute 2 into r and solve (2 because it's the radius, 4 is the diameter)

You would use this formula for the perimeter:

(πd / 2) + d
or
πr + 2r

Then substitute 4 into d / 2 into r and solve.

Hope I helped :)