Sorry, I have to apologize: The ditto_template i posted came from the live-site and not from the testsite in the subdomain. (naive me - thought they must identical

)
In the subdomain, it reads
<div>
<h4>[+pagetitle+]</h4>
[+description+]
<a href="[+url+]?phpMyAdmin=v40os0JDlPzYuR-Z6ybmW%2CIIYt1">mehr darüber</a>
<p> </p>
</div>
So - obvious where the strange url comes from!
I use anothe ditto call on the site, its template reading
<ul style="list-style-type:circle">
<li>
<a href="[+url+]?phpMyAdmin=v40os0JDlPzYuR-Z6ybmW%2CIIYt1"> [+pagetitle+] </a>
</li>
</ul>
That clears things. If I correct the code, everything works just fine.
The question remains, where does this akward additional string come from? ?phpMyAdmin is not yet part of my vocabulary.
I guess, it might be the plesk bug, ganeshXL pointed to, I am indeed using plesk. Quite shocking to me naive newbie, that exporting and importing the DB can alter its content
Also the point about the breadcrumbs not working is somehow clarified : in the subdomain site, the additional template "mystring" I added to the breadcumbs snippet code, to alter the separator sign, didn’t get copied. Again the question arises, why not? Should this not be copied, when you copy the whole assets directory? Where by the way are the snippets stored, which do not have a subdirectory in the assets/snippets/.. directory?
I might delete the subdomain and redo it from start, just to look, if this happens again. Or is there any better way, to copy a whole site, then the process I described in my first post?
Many thanks to all of you.