www programming

I used /wp-admin to reset password (sometimes it does not say password wrong, I get just redirected home the startpage without beeing logged in)

What is also strange, that now my forum is not saving my login and I always have to login again.
Do you know a solution?

phpBB do not save cookies, and using just session, i assume because the cookie setting into your phpBB is wrong?
OR did you setup the option in phpBB ACP
Allow Remember Me option need to be set to YES and set remember me time maybe to 365 gg.
One of two above mentioned, should be the problem.
Which is the url?
if the url of your site is
mydomain.com
the cookie domain setting need to be .mydomain.com
if it is mysite.co.uk will be .mysite.co.uk
while the cookie path setting need to be a single slash /
if you change these settings, then logout and clean cookies by clicking into Delete cookies link, on the right link on phpBB bottom pages. Re-login

So my Wordpres Site is available under https://www.seven-ig.de
and my PHPBB Site is available under https://www.seven-ig.de/phpBB3/
I attached a screenshot of my cookie and the plugin settings.
Maybe you can see a mistake.

It seem ok about cookies, but i can't create an account test may because i do not understand the language, it return me error when i try to reg in phpBB, could you create an account to test via wp?
Send me via pm details please.

I've sent you a pm

As said in the pm here are the screens