Error message

• Warning: file_put_contents(sites/all/themes/theme935/less/style.less.cache): failed to open stream: Permission denied in auto_less_compile() (line 42 of /var/www/clients/client0/web15/web/sites/all/themes/theme935/includes/less-compile.php).
• Warning: file_put_contents(sites/all/themes/theme935/css/style.css): failed to open stream: Permission denied in auto_less_compile() (line 43 of /var/www/clients/client0/web15/web/sites/all/themes/theme935/includes/less-compile.php).
• Warning: file_put_contents(sites/all/themes/theme935/less/style-mobile.less.cache): failed to open stream: Permission denied in auto_less_compile() (line 42 of /var/www/clients/client0/web15/web/sites/all/themes/theme935/includes/less-compile.php).
• Warning: file_put_contents(sites/all/themes/theme935/css/style-mobile.css): failed to open stream: Permission denied in auto_less_compile() (line 43 of /var/www/clients/client0/web15/web/sites/all/themes/theme935/includes/less-compile.php).
• Notice: Undefined index: #node_edit_form in i18n_menu_overview_form_alter() (line 13 of /var/www/clients/client0/web15/web/sites/all/modules/i18n_menu_overview/i18n_menu_overview.menu_settings.inc).
• Warning: unlink(sites/all/modules/tm_follow/css/tm_follow.css): Permission denied in drupal_unlink() (line 2282 of /var/www/clients/client0/web15/web/includes/file.inc).