nginx letsencrypt PHP错误index.php无法正确加载

i got a problem with my litecart system and lets encrypt.

Since i installed successfully lets encrypt, my index.php started acting like a idiot, it's giving my always a 404 not found. it redirects me to h t t p s: / / m y s it e . d e / d e /

Obviously it's a problem with setting up the locale language (german), at the first moment i thought it was a direct problem with lets encrypt (only warnings in the nginx error log)

what i tried:

installed LEMP and LAMP

chmod -R 777 all files

chown www-data:www-data all files

same result with apache2

nginx error log

 2019/03/21 10:03:26 [error] 17172#17172: *65 FastCGI sent in stderr: "PHP message: Warning: Warning: Failed setting locale d e _ D E . utf8,de_DE.UTF-8,german for de in ~/includes/library/lib_language.inc.php on line 110
 ↠~/includes/library/lib_language.inc.php on line 23 in set()
↠~/includes/classes/system.inc.php on line 38 in forward_static_call()
↠~/includes/app_header.inc.php on line 32 in run()
↠~/admin/index.php on line 2 in require_once()

any ideas or hints?