I had to edit .htaccess to get the 384 Mega memory,

So what did you change??

I simply put the line with
php_value memory_limit 384M
in the first line of my .htacces and left the rest as it was, now it works!

May be related to the way php is installed as explained in https://support.tigertech.net/php-value

Servers run PHP in "CGI mode" as recommended by the PHP developers (not as an Apache module), can't use "php_value" >or "php_flag" commands in .htaccess files. If you try to do so, you'll see an "internal server error" message.

Using php_flag or php_value in .htaccess files
Some PHP scripts suggest using "php_value" or "php_flag" commands in .htaccess files, as in this example:

    php_value  include_path         ".:/usr/local/lib/php" 
    php_flag   display_errors       Off
    php_value  upload_max_filesize  2M

I think the culprit is

<IfModule mod_php5.c>

which needs to be replaced with

<IfModule mod_php7.c>

if you're running PHP 7.

I replaced it and it works like a charm!

Instance name
b2evo 
b2evolution version
6.10.2-stable released on 06/20/18 
You are running the latest stable version of b2evolution.

Media directory
OK - /www/htdocs/w011e122/spanien-umzug/b2evolution/media/ 
.htaccess
/www/htdocs/w011e122/spanien-umzug/b2evolution/.htaccess 
.htaccess is identical to sample.htaccess
Install folder
Deleted 
Internal b2evo charset
utf-8 
Blog count
2 
Caching
Cache directory
OK - /www/htdocs/w011e122/spanien-umzug/b2evolution/_cache/ 
Cache folder size
9.0 KB 
General caching
Disabled 
Blog's cache setting
0 enabled /2 blogs 
Time
Server time
07/15/18 - 02:06:58 am 
GMT / UTC time
07/15/18 - 12:06:58 am 
b2evolution time
07/15/18 - 02:06:58 am 
MySQL
MySQL version
5.7.21-nmm1-log 
MySQL UTF-8 support
Yes 
PHP
PHP running as USER:
w011e122 (uid 1608) 
PHP running as GROUP:
w011e122 (gid 1183) 
PHP version
7.1.11-nmm1  
PHP register_globals
Off 
PHP allow_url_include
On 
When enabled, this feature is known to facilitate hacking exploits in any PHP application.

b2evolution includes additional measures in order not to be affected by this. However, for maximum security, we still recommend disabling this PHP feature.

If possible, change this setting to allow_url_include = Off in your php.ini or ask your hosting provider about it.

PHP Magic Quotes
Off 
PHP upload_max_filesize
32M 
PHP post_max_size
40M 
PHP memory_limit
384M 
PHP forced max_execution_time
600 seconds 
b2evolution was able to request more time (than the default 30 seconds) to execute complex tasks.
PHP mbstring extension
Loaded 
PHP XML extension
Loaded 
PHP IMAP extension
Loaded 
PHP opcode cache
none 
Using an opcode cache allows all your PHP scripts to run faster by caching a "compiled" (opcode) version of the scripts instead of recompiling everything at every page load. Several opcode caches are available. We recommend APC (which is included with PHP starting from PHP 7).
PHP user cache
none 
Using an user cache allows b2evolution to store some cached data (Block Cache) in memory instead of regenerated the blocks at each page load. Several user caches are available. We recommend APCu (which needs to be enabled separately from APC, starting from PHP 7).
GD Library (image handling)
GD Library version
bundled (2.1.0 compatible) 
GD JPG Support
Read/Write 
GD PNG Support
Read/Write 
GD GIF Support
Read/Write 
GD FreeType Support
Yes 
APIs
REST API
OK 
http://spanien-umzug.com/api/v6/collections
XML-RPC
OK 
http://spanien-umzug.com/xmlrpc.php
AJAX anon_async.php
OK 
http://spanien-umzug.com/htsrv/anon_async.php?action=test_api
AJAX async.php
OK 
http://spanien-umzug.com/htsrv/async.php?action=test_api
AJAX action.php
OK 
http://spanien-umzug.com/htsrv/action.php?mname=test_api
AJAX call_plugin.php
OK 
http://spanien-umzug.com/htsrv/call_plugin.php?plugin_ID=-1&method=test_api

I think most people use PHP 7 now and the sample .htaccess could be modified in the distribution file too.