Can you please post the config.php section where username and password and DB details (no DB password!) are listed?

// Basic Setup

$databasetype = 'postgres'; // ADOdb database driver - valid values are mysql, mysqli, odbc_mssql, mssql_n, odbtp or postgres

$databasename = 'umfragepiratenndsde'; // The name of the database that we will create
$databaseuser = 'umfragepiratenndsde'; // The name of a user with rights to create db (or if db already exists, then rights within that db)

$dbprefix = 'lime'; // A global prefix that can be added to all LimeSurvey tables. Use this if you are sharing
// a database with other applications. Suggested prefix is 'lime'

// File Locations
$rooturl = "https://umfrage.piraten-nds.de"; // The root web url for your limesurvey installation (without a trailing slash).
// The double quotes (") are important.

$rootdir = dirname(FILE); // This is the physical disk location for your limesurvey installation. Normally you don't have to touch this

// Installation Setup
$defaultuser = 'admin'; // This is the username when LimeSurvey is installed and the administration user is created on installation
$defaultpass = 'password'; // This is the password for the administration user when LimeSurvey is installed

// Debug Settings
$debug = 1; // Set this to 1 if you are looking for errors. If you still get no errors after enabling this

ok, try the following:

delete all tables from the existing database, restore the /admin/install dir.
Edit createdb.php

Before line:
if($createdbtype=='postgres' && version_compare($connect->pgVersion, '9') >= 0)

insert the following line:

echo $connect->pgVersion; die();

When starting the installation now and it is trying to populate the data it should now show some kind of information.
Can you tell us what is shown?

Feedback please?

9.1

Thank you. Now move the inserted line right after the line.

$connect->execute("ALTER DATABASE {$dbname} SET bytea_output='escape';");

and run the install again.

Do you still get the same output?

Yes, still the same output.

OK, revert all changes and run the command on your Postgres LimeSurvey database manually.

ALTER DATABASE {$dbname} SET bytea_output='escape';

Replace {$dbname} with your actual limesurvey database name. Let us know if you get any errors if you run this.

If you get not error run the installation again (make sure the database exists and is empty) and check if you can login now.

Ok, I got an error, because the user was not owner of the database.
After making the user owner, the installation and login works.

Maybe you could add an output for database errors, so the user is notified of these mishaps.

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=8785