Drupal 7.x

Hi all, I am running a website for a school. I detected a problem, that is, when users authenticate, me as admin included, they cannot reach the homepage and get a 502 bad gateway error. 

the only way to go to the home page is logging out

There is no visitor counter or any other service pointing to other server, or at least i think so. Any suggestion where to start ?

This is my config D7.91

php 7.4

max_execution_time 240

max input time 90

memory limit 1024

max input vars 1000

output buffering

post max size 25m

Hello,
as mentioned in the post title, I'm new to drupal. I used to build websites with WordPress but I need to apply corrections to an existing website built with drupal 7 and bootstrap 3.
I've found the CSS file to apply style changes, so this part is OK.
I've also access to the drupal dashboard but not in a full way (and I have access to the FTP server).
Now, for example, I try to modify a table to delete a column and add a new one. I'm a bit confused with the way to do that ans espacially what file(s) I have to modify.

I have drupal multisite whitch I want to update from version 7.89 to 7.91, but when I copy new files, got blank page. It's the same with version 7.90. Data is stored in postgree data base 9.5.23 version. Site is runing on php 7.0. There is one database for all sites, and each site has it's own scheme. 

I was thinking mybe i have to clear cache, so i open update.php, and it shows this error:

I have a content type in which i have added a Node reference.But i dont know why i can only see 25 nodes whereas i have about 3000 nodes that should be appearing in the select list.Can you please suggest me quickly.

Thank you.

Hello,

We´re looking to hire services to migrate a D7 site to D9. Site is www.valvulita.com The migration service should include migrating content, users and modules (all of them contributed, standard modules. Contractors should have experience in previous drupal migrations.

If interested please send an email to francesco@valvulita.com for further information. We´re looking to select a provider quickly.

Best Regards.