Drupal 8.x

Is there any module for messages between users in Drupal 8 or 9. Actually I want to make this with Drupal core without module. Is this possible. Thanks for support 

Randomly, translated content is showing a 404 page.
Also, unable to access translated content in Admin content listing view, it's redirecting to default the English language on clicking edit.

The wrong URL is being generated in the edit for e.g

1. Italian(langcode - "it") =>  /in/ode/[nid]/edit
2. Nepali(langcode - "ne") =>  /in/ode/[nid]/edit

I have faced the above issue for Italian and Nepali language so far, unable to understand what's wrong with these two languages.

I'm trying to setting up a real estate portal and I need to figure out which way might be the best one for the following operations with exposed filters views, searching, facet, etc.

I am very undecided on which way to choose. My instinct would be to do it through a referenced node for each house, but I was considering the hypothesis (to make it more convenient and faster for the user to enter data) the use of Paragraph.

I am trying to customize the user registration page of the website (also the login page). My main complaint is the default user registration page looking awful (yes, it is functional, but does not fit with the rest of the theme and the way it displays the logo at the top - it does not work for my square logo) on my site - for most other websites this is perfectly fine.

I have Googles for instructions on how to do this, but everything I got stopped at Drupal 7.

I want:

Hi,

We currently have 2 sites built with Drupal that share the same codebase but the sites are built separately. They are for two separate brands that do essentially the same thing so the sites are very similar including the same content copied and pasted as they have a separate database per brand. We are now looking to add another 10 brands (which was never the plan when the site was built in Drupal) so exploring better ways of working.

Goals:

Build the page once and publish across all sites