No problem, German is my fourth language, only speaking and understanding, will never write in German on a public forum.
Your timeline confirms my original suspicion: you have 4 buttons on that timeline. Two of them are pausing at 1,5secs, the top one in the timeline is pausing at 2 secs. This means that the playhead will stop at 1.5secs, no further objects will appear that are timed after the pausing, until one of the two buttons pausing at 1.5secs is clicked (provided it has a Continue command). You may be confused by the fact that slide audio continues, it could be stopped as well but the default setting which you apparently didn't change is to continue playing audio. That is why you continue to hear the audio.
What do you need those first 3 buttons to do? They seem to be timed till the end of the slide. If you want all objects to appear, you have two possiblities:
- Move the pausing point of the first 3 to the right, after the appearance of the last object, which is also a button with another pausing point. You can either drag the pausing point or use the Timing Properties panel. Since I am not sure about the goal of those 3 buttons, I recommend to have them pause at exactly the same time as the fourth, last button which is about 28;8secs.
- Take out the pausing for the first 3 buttons. You can use the Timing Properties panel to take out the pause. I suspect this will be the best solution. The last button will prevent the playhead from proceeding, and all the objects have appeared synchronized with the slide audio.