Redirect, slow page Speed

Hi WP-experts,
I’ve got a page speed problem as you can see on the following screenshots:
.de https://imageshack.us/photo/my-images/546/websitespeedde.jpg/
.com works fine https://imageshack.us/photo/my-images/211/websitespeedcom.jpg/

Here’s the website: https://www.pixories.de https://www.pixories.com

Overview about installed plugins https://imageshack.us/photo/my-images/35/websiteinstalledplugins.jpg/

.htaccess

<IfModule mod_headers.c>
Header append Vary Accept-Encoding
</IfModule>

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]

Any hints were the problem may come from? What can I provide to help you/us find a solution?

Thanks

https://www.ads-software.com/extend/plugins/wordpress-mu-domain-mapping/