Problem with the theme

Hello , first of all a normal user (gamer) registered on the site can change the profile picture as well as the background picture to any other user. The other problem is that when i try to activate the plugin “arcane types” i get a fatal error with the following message : “Fatal error: Cannot redeclare class Arcane_Types in /home/blackfi2/public_html/wp-content/plugins/arcane_custom_post_types/arcane_custom_post_types.php on line 14”.I hope you will resolve this problem as soon as possible . Thank you!