You can make a fire with: magnification glasses, some dry leaves, pieces of paper or small tree's branches.
First Put some pieces of paper or dry leaves on the ground, then use the magnification glasses to the sunlight cross through the glasses and make a small spark that can burn the paper.
For a Shelter you can use tree's wood or big tree's branches, leaves or plastic and strings.
First make a two triangules with the wood and tie together making a knot with the strings , second cover this with leaves or plastic, use glue or nails with a hummer to do it.
To make a Signal you can do a big fire with dry leaves and wood or tie some tree's branche together with some clothes and make a flat.