Hello @JensBoelte Thanks a lot for your quick reply! 
I followed your advice and put all the training / reminder routines in just one routine. Now, however, I have some other issues.
So to first show you, here is how one Training routine looks like:
I made this Excel sheet which includes the duration values (you can for now just focus on coloumn A to F, the rest is for Reminder routine and the logic is basically the same). What I did here is, I put the duration of each sound clip manually and I put those values in a way that it matches with the duration of a certain shape (e.g when dur_story_1 is 90, dur_cue_circle is also 90 and the rest of the durations in that row is zero, so nothing else will appear. Only Sound 1 and the Shape Circle will appear. When the loop iterates, then it moves on to other pairs)
I indexed the duration as, e.g. $dur_story_1 in the properties of “story_1” variable above. And did the same for all other stimuli in the loop.
So, my first question is… I would actually like it better, if participant press a button after a sound clip ends, to move on to the next one. It can be easily done when the routines are separate but when everything is in one routine, I couldn’t come up with a solution. Is there a way to set the button press as something that moves the loop forward? (If I’m making sense). If so, how could I adjust my excel table for this – right now, it is all based on the duration of the sound clips…
And to mention another thing, to counterbalance, I create separate condition files for each participant (6 different files in total, the one above is the 1st version) and I found this code below, which reads a certain condition file based on the participant number: (This code is from frank.papenmeier, see this discussion here: Selecting condition files depending on participant number - #2 by frank.papenmeier so, thank you!)
And my condition files are located in a folder like this:
So, the second question: my understanding is if, let’s say I will have 15 participants, I have to create 15 of these to make the indexing work with that code? Or, would there be a, again, “more elegant” way to do so?
Sorry for this long message! And thank you again!