Hello, I’m kinda new to Cubase and I have a hard time to find a way to mark or label my timeline (Intro, Breakdown, Drop, Etc) in other words, time markers. Thanks in advance! 
Hi and welcome,
You can add a Marker track. In the Marker track you can add a Markers (+ button), which are points in time. Or you can add a Cycle Markers (++), which are time frames/areas/boxes. To do this, set the Left and Right locator to the area, where you want to add the Cycle Marker. And then trigger the function. The Cycle Marker is added to the place of the L/R Locators.
Another way is to use Arranger Track. There you can mark a time-boxes just by draw tool. The disadvantage is, you can’t jump to these events so simple, as you can do with Marker Tracks. The advantage is, you can rearrange your song easy just by settings new Arranger events chain in the Arranger editor.