Yes! Now it works. (nice)
This is starting to drift a bit from the basic question, but it’s interesting.
The database starts to get more complicated with a number of relational tables.
When this database was created.
How was it planned?
Are all the values manually entered?
or did you do the structure first and then some kind of import of all the information?
Thank you!
Yes! It works (The little I have tested) 
(but take some time to do)
Next time I try again
Yes - to create the source information, but not all information should go to the same table.
RNDGen generated random information to a csv file (or ??? - format)
How was that information read into LO Base? (import table for table or all tables at the same time? or manually)
It is always best to design the empty database tables, indices and relations first. For one-off operations, I copy from Calc and paste to the Base table icon. Invalid data (incomplete rows, wrong types, duplicates) raise errors and don’t get into the database. Pasting arbitrary sheet trash into Base and then trying to get the structure right is cumbersome.
For regular csv import, such as bank accounts, I use prepared HSQL text tables together with SQL views and a fairly simple Basic macro. This is by far easier to do than with Calc, as long as the csv structure does not change.
_xlfn means, that it is a function that is unknown to LibreOffice. In this case it is the Image function IMAGE function - Microsoft Support.
You can try this: Copy the link itself (full https://…). Then go to Insert > Image and paste the link into the “File” field. Mark the option “Link”.
Yes! it works. (thank you!) the image is inserted in a cell.
Is it possible to write a formula to do this automatically?
I can export the .xlsx-file to a csv-file and pick out the urls.
But how to activate all these URLs automatically?