Give solution to my broken wbesite after secring with SSL

I have installed SSL on my website, but immediately after installing, my website have broken(the layouts have completely been changed). I am worried for this.

I have checked by changing the theme to default theme and also checked by deactivating all my plugins and checked but the problem is still there.

When I checked the site health status, the following critical issue is shown.

Background updates ensure that WordPress can auto-update if a security update is released for the version you are currently using.

Error A plugin has prevented updates by disabling wp_version_check().
Passed No version control systems were detected.
Passed Your installation of WordPress doesn’t require FTP credentials to perform updates.
Error Some files are not writable by WordPress:
xmlrpc.php
wp-blog-header.php
readme.html
wp-signup.php
index.php
wp-cron.php
wp-login.php
wp-settings.php
license.txt
wp-mail.php
wp-links-opml.php
wp-load.php
wp-includes/class-wp-user-query.php
wp-includes/l10n.php
wp-includes/date.php
wp-includes/images/blank.gif
wp-includes/images/down_arrow.gif
wp-includes/images/spinner.gif
wp-includes/images/media/interactive.png
wp-includes/images/media/default.png
…

Kindly provide me the solution to bring back my site to normal.

The page I need help with: [log in to see the link]