Problems with SEARCH

My site (still under construction) is berlin-explorer.org
My theme is Twenty TwentyFive.
The Query Loop Block in the Search Result Template is set to DEFAULT

And here is my problem, that I have trying trying to fix during the last week.
I have only one page (HOMEPAGE) and 5 Posts, the titles of which are: The Wedding (Zoning); Wedding 2; Beginning of the 18th cent. Overview; Beginning of the 18th cent.

Whatever I enter in the search bar, I get only one result, either the title of a post, or the message that “nothing was found”. This gives rise to the

1rst question: shouldn’t I in certain cases have more than one result? For instance when the title of several posts contain the word that I entered in the search bar?

2nd question.
When I enter “wedding 2”, the result is (as expected) the post Wedding 2.
When I enter “the wedding”, the result is (as expected) the post The Wedding (Zoning)
When I enter “wedding” the result is not, as I would expect, both Wedding 2 and The Wedding (Zoning), but only Wedding 2.

When I enter “the”, I would expect the results to be on several lines The Wedding, Beginning of the 18. cent. Overview, AND Beginning of the 19. cent. Overview.
On the contrary I get as result only Beginning of 19th. Cent. Overview.

When I enter “beginning of the 18th cent. overview” and respectively “beginning of the 19th cent. overview” the result is (as expected) Beginning of the 18th cent. Oerview and respectively Beginning of the 19th cent. Overview

But, when I enter: “beginning”, “beginning of the”, “overview” or “the”, i always get as unique result the post title Beginning of the 18th cent. overview.

Am I wrong when I expect a list of all the post-titles that contain the entered word?
What should I do in order to correct this behavior?
Do search plugins use the Query Loop of the theme, or execute the search using their own code?

Thank you for you patience and your help.