Solving a Problem generate a second one !

I want to upload a plugin , and i receive Error , and then when i search on www.remarpro.com it tells me That i need to add http.php , so when i upload it to my wp-includes it shows a new error :

Fatal error: Cannot redeclare class WP_Http in /home/content/49/11533349/html/wp-includes/class-http.php on line 34

when i tried to delete it i’ve received a new error : Warning: require(/home/content/49/11533349/html/wp-includes/http.php) [function.require]: failed to open stream: No such file or directory in /home/content/49/11533349/html/wp-settings.php on line 141

Fatal error: require() [function.require]: Failed opening required ‘/home/content/49/11533349/html/wp-includes/http.php’ (include_path=’.:/usr/local/php5_3/lib/php’) in /home/content/49/11533349/html/wp-settings.php on line 141

Please i need your help !!