Thank you for the answers!
I would like to gather a lot of information before I buy something and of course I know the saying that if you buy cheap, you buy twice. That's why I'm looking for information about which manufacturers offer reasonable concertinas. I'm not interested in the cheapest instruments made in China, possibly even made by children.
I know the difference between Anglo, English and Duet, but I'm not yet sure which type of concertina suits what I like to play.
What do I like to play:
A few years ago I took clarinet lessons from a jazz musician. There I learned pieces like "Mack The Knife", "Fly me to the moon", "What shall I do with a drunken Sailor" etc. I enjoy such pieces. But I also love to play simple folk songs or children's songs and give them a little swing and occasionally sprinkle in a blue note (that will probably be difficult with an Anglo, right?). Right now I'm playing these things on a tinwhistle. (The clarinet was too difficult for me. I gave it up again).
For this purpose I am looking for a suitable concertina that does not squeak like a cheap toy and does not dismantle into its individual parts after a few years.
I am not yet sure, whether I can enjoy this new freedom. I'm the workhorse type