'Perfect Storm' situation! 2.8 won't run under PHP 7.0.x and higher ... first version of Moodle that would is 3.0.x.
Suggest backing up what you can before going further ... safest way are 2 command line only tools ... tar and mysqldump .. neither of those use PHP nor old Moodle code no longer compat.
Must have ssh/command line access site and find where code and moodledata is located + DB name, DB user, DB password. All that info is in config.php of your site.
To backup database with no corruption:
mysqldump -u 'dbuser' -p'dbpass' 'dbname' > moodle28.sql
you replace values in '' above with those seen in config.php
To backup moodledata .. path is in config.php
From your home directory and in ssh:
tar -cvf moodledata.tar /path/to/moodledata
To backup moodle code ... probably in /home/customer/public_html/? Use your cpanel or other tool that can browse files to locate.
From home directory and in ssh
tar -cvf moodle28code.tar /path/to/moodlecode
Download both 'tar' files and the .sql dump to your local machine.
Do that first, then we can figure out rest!
'SoS', Ken