first of all you can split every face of its faces into 2 right angle triangle then you are gonna find the height of that triangle by c²=a²+b²
i will be 5²=4²+b²
so b =3 (if you don't know how to solve that equation above just ask me)
okay now we have the height and base
so the are of that triangle will be 0.5 *4*3=6
so the area of right triangle is 6 and one face of pyramid faces has 2 triangles like this so the whole are will be no of faces *2*6=
4*2*6=48 m²