I have already created a lot of worlds with the respective seeds from the Internet, but a different world is always created and if I then look at the seed in the settings, there's a completely different value.
e.g. I create a world with the seed 75834848848484738484 but in the settings it is e.g. -6,737,384,747,373.
The seeds I enter are 1. Compatible with my MC version and 2. Written correctly.
Then what am I doing wrong?
Are these Java Edition Seeds? You don't go on the Pocket Edition. And instead of wasting 1 minute to go into the settings, you can just type / seed in the chat and the seed will be shown.