Installing and upgrading help

Hi Leon, and thanks for your response.
In the config.php, the configuration is: $CFG->wwwroot = 'https://mydomain.net';
When I access to the internet navigator, I write mydomain.net or https://mydomain.net and I see the same page without any css.
I contacted with my server provider to ask about this, and they say, it's a compatibility problem between the server and this moodle version and give to me this instructions:
(I used a translator from Spanish to English, I hope can understand me)

1 -Create a file 'php.ini' with the corrected parameter: cgi.fix_pathinfo = 0 (This I can do it)

2 -Create symbolic links in all folders of the installation with the following command via SSH:

find -type d -exec ln -s $ PWD / php.ini {} /php.ini \; (This I don't know how to do via SSH)

3 -Depending on the Moodle version, you should also review 'config.php' and activate the slash arguments, with the following parameter:

$ CFG-> slasharguments = true; (This is not in my config.php but can do it)

After this, the problem of links is corrected, which would allow the CMS to be used while the open incident is not closed.

I don't know if this is the solution to my problem.

The website is now with the ssl certificate and it's working ok.

I don't know what to do.
Can you help me again, please?

Thanks for your response. I deleted the cache and localcache folders content and haved the same page with plain text.
Please, have another suggestion?