I am doing text with a lightsource behind. I am following a tutorial. The text casts shadows like it should but the light passes through the letters, I dont wont that, they should be solid. I have missed something very basic. The letters in the tutorial looks more 3D also, mine are flat, 2D.
Your cropped screenshot* tells us nothing about your workflow or how you set up your layers. Select all layers, press the U key twice, then embed your screenshot or screenshots so we can see what you have done to the layers.
When you have problems with a tutorial we need to have a link to the tutorial so we can see what you are dealing with. Most of the new tutorials on the web are prepared by enthusiasts, most of those are recipes that they have copied from somewhere, many of them include inefficient workflows or workflows that will only work with a specific shot, and a great majority of the tutorials are very poorly explained and steps are left out.
If the tutorial you are watching looks more 3D then you have not followed the same steps. Maybe the author is using the C4D rendering engine. Your screenshot just looks like you have the volumetric lighting effect stacked in the wrong order. Use your system shortcuts** to take your screenshots and explain your workflow, point us to the tutorial, and we can probably help.
* The "Drag & Drop here..." area is buggy and should not be used to share images. Please use the toolbar or just drag your images to the reply field.
** Mac shortcut for a screenshot Shift + Ctrl + 3
Windows shortcut for a screenshot Windows Logo Key + PrtScn if you don't have a PrtScn key use Fn + Windows logo key + Space Bar
Screenshots are usually in your Pictures folder or on your desktop.