How can I add more reflections to my glass material? I'm trying to reach a render like the one on the image below. It's a prism as you can see, and I already made the elements, but the reflections aren't the same. 

Maybe it's the material, but I do not know. I already tried changing the object's position and lighting, but it didn't help. So I think it could be the material
Your material setup is wrong. On first glance you are feeding shader output to glass node color input.

Leave only 1 glass node connected to Shader output, delete the rest.

If you then need more reflections you can mix in a Glossy shader with Fresnel node.