Run multiple queries during drilldown and use selected elements from visual in SQL-where clause

I came a bit closer to my goal creating an m-query for our postgres database using parameter, but the Postgres.Database function complains about a string, if it was produced with Text.Combine. What am I doing wrong here or is there a problem?

see details :

This m-query ,which has no syntax erros,  gives the following error, it looks like the postgres DB does not like the string made of substrings and parameter :

But if I use a string which was not a result of text.Combine then it works, the following works.

But I need Text.Combine to get my parameter in.

What am I doing wrong here ? 

If some of you gurus sees my mistake, please give me a hint.

Many thanks in advance.