Setup not found during installation (right after "Welcome to Neos"-screen)

Hi everyone,

I am currently trying to install Neos for the first time (on a shared server). After redirecting the domain to the Subfolder by editing the .htaccess-file the Welcome-screen appeares.

For some reason it says There is no database connection yet or the Neos database schema has not been created., and a note below saying #0: An error occurred in the Database Abstraction Layer.

If I get all the how-to-install-neos-instructions right, I simply should click the blue Go to setup-button now.

Unfortunately the browser seems to got lost (404 Not Found / The requested URL /setup was not found on this server.)

Does anybody know what I should do as a next step?

Kind regards