Ok, i added the Grant Type and made a note into my book at page 190. Grant Types: authorization_code.
Meanwhile i found your doc at https://gluu.org/docs/gluu-server/4.3/integration/sswebapps/openidc-rp/
which contains the information **Grant Types: authorization_code**.
Now it's working! I get a Login Page and i see the Env Vars after successful login.
Thank You for your help Shakil,