Where should i manage accounts?

i discovered that it's no implemented -.- will you implement this^

I guess that's not clearly stated in any documentation, unless you've been following the discussions here. As the foreword at http://kepp.net/phpbb3/ suggests, user management is only supported through phpBB. I generally recommend never deleting users, through the years I have seen bugs in both Drupal and phpBB because some modules / mods do not take this into consideration. If you disable them, it should have the same effect.

It's a design decision, because phpBB 3's user profiles are much richer than Drupal's. If anyone submits a patch that reverses this, or provides funding, I'll certainly consider it. But it is not on my personal todo list.