Hello there
Im having the 502 bad gateway,
I followed this guide
php-gd php-curl php-mbstring letsencrypt
#get file sorted
cd /tmp
wget https://download.owncloud.org/community/owncloud-9.1.0.tar.bz2
mkdir -p /var/www/owncloud
cp -R owncloud/* /var/www/owncloud
chown -R www-data: /var/www/owncloud
#setup database
mysql -p
CREATE DATABASE owncloud;
CREATE USER ‘newuser’@‘localhost’ IDENTIFIED BY ‘password’;
GRANT ALL PRIVILEGES ON * . * TO ‘newuser’@‘localhost’;
FLUSH PRIVILEGES;
exit
#gen certs
letsencrypt certonly --standalone -d cloud.opengeek
#setup webserver
copy config
vi /etc/nginx/conf.d/
Changed the port of Apache to 8080 because it interfears with nginx port.
Nginx conf file;
upstream php-handler {
server unix:/var/run/php/php7.0-fpm.sock;
}
server {
listen 80;
server_name cloud;
return 301 $server_name$request_uri;
}
server {
listen 443 ssl;
server_name cloud.example;
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
Path to the root of your installation
root /var/www/owncloud/;
set max upload size
client_max_body_size 10G;
fastcgi_buffers 64 4K;
Disable gzip to avoid the removal of the ETag header
gzip off;
Uncomment if your server is build with the ngx_pagespeed module
This module is currently not supported.
#pagespeed off;
rewrite ^/caldav(.)$ /remote.php/caldav$1 redirect;
rewrite ^/carddav(.)$ /remote.php/carddav$1 redirect;
rewrite ^/webdav(.*)$ /remote.php/webdav$1 redirect;
index index.php;
error_page 403 /core/templates/403.php;
error_page 404 /core/templates/404.php;
location = /robots.txt {
allow all;
log_not_found off;
access_log off;
}
location ~ ^/(?:.htaccess|data|config|db_structure.xml|README){
deny all;
}
location / {
# The following 2 rules are only needed with webfinger
rewrite ^/.well-known/host-meta /public.php?service=host-meta last;
rewrite ^/.well-known/host-meta.json /public.php?service=host-meta-json last;
rewrite ^/.well-known/carddav /remote.php/carddav/ redirect;
rewrite ^/.well-known/caldav /remote.php/caldav/ redirect;
rewrite ^(/core/doc/[^\/]+/)$ $1/index.html;
try_files $uri $uri/ =404;
}
location ~ .php(?:$|/) {
fastcgi_split_path_info ^(.+.php)(/.+)$;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_INFO $fastcgi_path_info;
fastcgi_param HTTPS on;
fastcgi_pass php-handler;
fastcgi_intercept_errors on;
}
Adding the cache control header for js and css files
Make sure it is BELOW the location ~ .php(?:$|/) { block
location ~* .(?:css|js)$ {
add_header Cache-Control “public, max-age=7200”;
# Add headers to serve security related headers
add_header Strict-Transport-Security “max-age=15768000; includeSubDomains; preload;”;
add_header X-Content-Type-Options nosniff;
add_header X-Frame-Options “SAMEORIGIN”;
add_header X-XSS-Protection “1; mode=block”;
add_header X-Robots-Tag none;
# Optional: Don’t log access to assets
access_log off;
}
Optional: Don’t log access to other assets
location ~* .(?:jpg|jpeg|gif|bmp|ico|png|swf)$ {
access_log off;
}
}
I have no clue what is causing this 502
I dont know where to look 
Hope you can help me out!