Transparent Material makes Mesh invisible

I made a Tree Model with Blender and a Leaf texture with Gimp and exported both to UE4.
Then i made the leaf texture Transparent and applied the Material to the Tree. But this made the Leaf parts of the Mesh invislbe.

I hope someone can help me.
PS: My english is bad. If someone has problems understanding my Question, i will try to express myself more clearly.

Hey, you should enable the two sided material option on the material editor

For anyone who is reading this in the future, i didn’t UV unwrap correct.