I precisely followed a tutorial step-by-step but the graph in the video had only one line and it was shaped differently. I know the green line represents position and the blue one is rotation, but I only want to see one of them at a time. How do I fix this?
Right-click in the Graph Editor and change the selection. You are looking at all animated properties.
It also looks like you are animating the Value graph. That is almost always the wrong graph to be editing. Value graphs are completely useless for animating Position and only marginally useful for animation Rotation and Scale.
Also, when having problems with a tutorial, please provide a link. Most of the AE tutorials you find with a web search are prepared by enthusiasts and the workflows and explanation often leave a lot to be desired.
Maybe this tutorial will give you some 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. If you can't see the screenshot before you click "post" it is a pain for us to see what is going on in your project.