Thank you so much for your response.
Problem partially resolved ("geen commentaren" removed). I still cannot fix that:
Blockquote
Also, for a weird reason, some merged string values look as they should (so with "/" divider) but others don't.
For example, final result for the fourth record is:
"Steeds zeer vriendelijkZonder problemen"
but should be:
"Steeds zeer vriendelijk/Zonder problemen"
I cannot get my head around it 
Can you help?
Slavek
P.S. I really wanted to use reprex but I have some issues which have not been resolved: https://forum.posit.co/t/a-good-chance-to-set-up-a-reprex/24357/3 so I follow your suggestion (Search results for 'datapasta topic:22701' - Posit Community) and use datapasta with small samples instead.
I have provided a sample with a view variables previously but solutions given on this excellent forum were not 100% helpful without taking into account the entire data file (for example: ISSUE 1 in here Mutate (not) all plus stringr issues was a result of that)
I'm still learning (no professional training or previous experience with R) but believe me, I always try to solve the problems myself first.
I really appreciate your help and I admire your knowledge!
I think this forum is the best way of finding solutions and the most helpful forum I have found in my career!