( URGENT PLEASE HELP !!! ) : ERROR 550 and many bugs after try to fix

Hello,
Can anyone help me pls ? I can give you the access to my web, I just need it for my graduation project.
Thank you ! My problem :
It's been 3 days that I have a error 500 for my website and my admin wp page. I try every single tutorial of OVH and what the assistant told me to do, but it didnt work. And then I try all the tutorial that I could found on internet, and the result now is my web is a blank, and my admin wp page become :


Fatal error: Uncaught Error: Call to undefined function __() in /home/haibiny/www/wp-includes/class-wp-taxonomy.php:607 Stack trace: #0 /home/haibiny/www/wp-includes/taxonomy.php(716): WP_Taxonomy::get_default_labels() #1 /home/haibiny/www/wp-includes/class-wp-taxonomy.php(486): get_taxonomy_labels(Object(WP_Taxonomy)) #2 /home/haibiny/www/wp-includes/class-wp-taxonomy.php(290): WP_Taxonomy->set_props('post', Array) #3 /home/haibiny/www/wp-includes/taxonomy.php(532): WP_Taxonomy->__construct('category', 'post', Array) #4 /home/haibiny/www/wp-includes/taxonomy.php(82): register_taxonomy('category', 'post', Array) #5 /home/haibiny/www/wp-settings.php(499): create_initial_taxonomies() #6 /home/haibiny/www/wp-config.php(96): require_once('/home/haibiny/w...') #7 /home/haibiny/www/wp-load.php(50): require_once('/home/haibiny/w...') #8 /home/haibiny/www/wp-admin/admin.php(34): require_once('/home/haibiny/w...') #9 /home/haibiny/www/wp-admin/index.php(10): require_once('/home/haibiny/w...') #10 {main} thrown in /home/haibiny/www/wp-includes/class-wp-taxonomy.php on line 607

Fatal error: Uncaught Error: Call to undefined function __() in /home/haibiny/www/wp-includes/class-wp-locale.php:148 Stack trace: #0 /home/haibiny/www/wp-includes/class-wp-locale.php(131): WP_Locale->init() #1 /home/haibiny/www/wp-includes/load.php(1568): WP_Locale->__construct() #2 /home/haibiny/www/wp-includes/class-wp-fatal-error-handler.php(176): wp_load_translations_early() #3 /home/haibiny/www/wp-includes/class-wp-fatal-error-handler.php(156): WP_Fatal_Error_Handler->display_default_error_template(Array, false) #4 /home/haibiny/www/wp-includes/class-wp-fatal-error-handler.php(60): WP_Fatal_Error_Handler->display_error_template(Array, false) #5 [internal function]: WP_Fatal_Error_Handler->handle() #6 {main} thrown in /home/haibiny/www/wp-includes/class-wp-locale.php on line 148