Cannot login to site Admin backend - Joomla! Forum - community, help and support

apologies if repeated not sure forum post. have installed extension joomgallery , in process of setting gallery, changed parameters , logged out of asmin. cannot log in admin backend. (also if enable login front end not working). when enter valid user , password, returns login panel again.
any welcome can no longer maintain website.
i discovered file in root directory unsure of , have attached . included fpa output below.
thanks
ken

problem description :: forum post assistant (v1.2.7) : 1st february 2017 wrote:joomla 3.x cannot login admin end

log/error message :: forum post assistant (v1.2.7) : 1st february 2017 wrote:no error reported form, reverts empty login form

forum post assistant (v1.2.7) : 1st february 2017 wrote:

basic environment :: wrote:joomla! instance :: .- ()
joomla! configured :: yes | writable (644) | owner: ashbournetownband.co.uk-2 (uid: 1/gid: 1) | group: ashbournetownband.co.uk-2 (gid: 1) | valid for: 1.6
configuration options :: offline: 0 | sef: 1 | sef suffix: 0 | sef rewrite: 0 | .htaccess/web.config: yes | gzip: 0 | cache: 0 | ftp layer: 0 | ssl: 0 | error reporting: default | site debug: 0 | database credentials present: yes

host configuration :: os: linux | os version: 2.6.32-642.6.2.el6.x86_64 | technology: x86_64 | web server: apache/2.4.23 (unix) | encoding: gzip, deflate | doc root: /home/cluster-sites/4/a/ashbournetownband.co.uk/public_html | system tmp writable: yes

php configuration :: version: 7.0.14 | php api: cgi-fcgi | session path writable: no | display errors: | error reporting: 22527 | log errors to: | last known error: | register globals: | magic quotes: | safe mode: | open base: | uploads: 1 | max. upload size: 2m | max. post size: 8m | max. input time: 60 | max. execution time: 30 | memory limit: 128m

mysql configuration :: version: 5.5.5-10.0.28-mariadb (client:mysqlnd 5.0.12-dev - 20150407 - $id: 241ae00989d1995ffcbbf63d579943635faf9972 $) | host: --protected-- (--protected--) | collation: utf8_general_ci (character set: utf8) | database size: 4.55 mib | #of tables: 107

detailed environment :: wrote:php extensions :: core (7.0.14) | date (7.0.14) | libxml (7.0.14) | openssl (7.0.14) | pcre (7.0.14) | zlib (7.0.14) | filter (7.0.14) | hash (1.0) | pcntl (7.0.14) | readline (7.0.14) | reflection (7.0.14) | spl (7.0.14) | session (7.0.14) | standard (7.0.14) | cgi-fcgi () | bcmath (7.0.14) | bz2 (7.0.14) | calendar (7.0.14) | ctype (7.0.14) | curl (7.0.14) | dom (20031129) | enchant (1.1.0) | mbstring (7.0.14) | fileinfo (1.0.5) | ftp (7.0.14) | gd (7.0.14) | gettext (7.0.14) | gmp (7.0.14) | iconv (7.0.14) | imap (7.0.14) | intl (1.1.0) | json (1.4.0) | ldap (7.0.14) | exif (1.4 $id: 8bdc0c8f27c2c9dd1f7551f1f9fe3ab57a06a4b1 $) | mcrypt (7.0.14) | mysqlnd (mysqlnd 5.0.12-dev - 20150407 - $id: 241ae00989d1995ffcbbf63d579943635faf9972 $) | odbc (7.0.14) | pdo (7.0.14) | pgsql (7.0.14) | phar (2.0.2) | posix (7.0.14) | pspell (7.0.14) | recode (7.0.14) | shmop (7.0.14) | simplexml (7.0.14) | soap (7.0.14) | sockets (7.0.14) | sqlite3 (0.7-dev) | sysvmsg (7.0.14) | sysvsem (7.0.14) | sysvshm (7.0.14) | tidy (7.0.14) | tokenizer (7.0.14) | xml (7.0.14) | xmlwriter (7.0.14) | xsl (7.0.14) | zip (1.13.5) | mysqli (7.0.14) | pdo_dblib (7.0.14) | pdo_mysql (7.0.14) | pdo_odbc (7.0.14) | pdo_pgsql (7.0.14) | pdo_sqlite (7.0.14) | wddx (7.0.14) | xmlreader (7.0.14) | xmlrpc (7.0.14) | zend engine (3.0.0) |
potential missing extensions :: mysql | suhosin |

switch user environment (experimental) :: php cgi: yes | server su: yes | php su: yes | custom su (litespeed/cloud/grid): yes
potential ownership issues: no

folder permissions :: wrote:core folders :: images/ (755) | components/ (755) | modules/ (755) | plugins/ (755) | language/ (755) | templates/ (755) | cache/ (755) | logs/ (755) | tmp/ (755) | administrator/components/ (755) | administrator/modules/ (755) | administrator/language/ (755) | administrator/templates/ (755) |

elevated permissions (first 10) ::

extensions discovered :: wrote:components :: site :: com_wrapper (3.0.0) | com_mailto (3.0.0) |
components :: admin :: com_modules (3.0.0) | com_postinstall (3.2.0) | com_users (3.0.0) | com_cache (3.0.0) | com_installer (3.0.0) | com_content (3.0.0) | com_login (3.0.0) | com_newsfeeds (3.0.0) | com_contenthistory (3.2.0) | com_jem (2.2.0) | com_menus (3.0.0) | com_admin (3.0.0) | com_finder (3.0.0) | com_plugins (3.0.0) | com_joomlaupdate (3.6.2) | com_ajax (3.2.0) | com_templates (3.0.0) | com_banners (3.0.0) | com_config (3.0.0) | com_tags (3.1.0) | com_languages (3.0.0) | com_redirect (3.0.0) | joomgallery (3.3.3) | joomgallery (3.3.3) | joomgallery (3.3.3) | com_search (3.0.0) | com_media (3.0.0) | com_checkin (3.0.0) | com_messages (3.0.0) | com_cpanel (3.0.0) | com_categories (3.0.0) |

modules :: site :: mod_articles_archive (3.0.0) | mod_syndicate (3.0.0) | mod_finder (3.0.0) | mod_breadcrumbs (3.0.0) | mod_related_items (3.0.0) | mod_stats (3.0.0) | mod_whosonline (3.0.0) | mod_articles_popular (3.0.0) | mod_feed (3.0.0) | mod_users_latest (3.0.0) | mod_jem_wide (2.2.0) | mod_articles_latest (3.0.0) | mod_tags_similar (3.1.0) | mod_tags_popular (3.1.0) | mod_jem (2.2.0) | mod_jem_banner (2.2.0) | mod_jem_jubilee (2.2.0) | mod_articles_categories (3.0.0) | mod_random_image (3.0.0) | mod_articles_news (3.0.0) | mod_menu (3.0.0) | mod_articles_category (3.0.0) | mod_jem_cal (2.2.0) | mod_custom (3.0.0) | mod_languages (3.5.0) | mod_jem_teaser (2.2.0) | mod_search (3.0.0) | mod_login (3.0.0) | mod_banners (3.0.0) | mod_wrapper (3.0.0) | mod_footer (3.0.0) |
modules :: admin :: mod_status (3.0.0) | mod_feed (3.0.0) | mod_logged (3.0.0) | mod_stats_admin (3.0.0) | mod_version (3.0.0) | mod_multilangstatus (3.0.0) | mod_submenu (3.0.0) | mod_popular (3.0.0) | mod_menu (3.0.0) | mod_title (3.0.0) | mod_custom (3.0.0) | mod_toolbar (3.0.0) | mod_login (3.0.0) | mod_quickicon (3.0.0) | mod_latest (3.0.0) |

plugins :: site :: plg_authentication_ldap (3.0.0) | plg_authentication_joomla (3.0.0) | plg_authentication_gmail (3.0.0) | plg_authentication_cookie (3.0.0) | plg_search_contacts (3.0.0) | plg_search_content (3.0.0) | plg_search_newsfeeds (3.0.0) | plg_search_categories (3.0.0) | plg_search_tags (3.0.0) | plg_search_jem (2.2.0) | plg_content_loadmodule (3.0.0) | plg_content_emailcloak (3.0.0) | plg_content_pagenavigation (3.0.0) | plg_content_pagebreak (3.0.0) | plg_content_joomla (3.0.0) | plg_content_jem (2.2.0) | plg_content_vote (3.0.0) | plg_content_finder (3.0.0) | plg_editors-xtd_article (3.0.0) | plg_editors-xtd_readmore (3.0.0) | plg_editors-xtd_pagebreak (3.0.0) | plg_editors-xtd_module (3.5.0) | plg_editors-xtd_image (3.0.0) | plg_system_languagecode (3.0.0) | plg_system_sef (3.0.0) | plg_system_p3p (3.0.0) | plg_system_stats (3.5.0) | plg_system_remember (3.0.0) | plg_system_languagefilter (3.0.0) | plg_system_updatenotification (3.5.0) | plg_system_debug (3.0.0) | plg_system_redirect (3.0.0) | plg_system_highlight (3.0.0) | plg_system_cache (3.0.0) | plg_system_logout (3.0.0) | plg_system_log (3.0.0) | plg_installer_urlinstaller (3.6.0) | plg_installer_folderinstaller (3.6.0) | plg_installer_webinstaller (1.1.0) | plg_installer_packageinstaller (3.6.0) | plg_captcha_recaptcha (3.4.0) | plg_user_contactcreator (3.0.0) | plg_user_joomla (3.0.0) | plg_user_profile (3.0.0) | plg_quickicon_extensionupdate (3.0.0) | plg_quickicon_joomlaupdate (3.0.0) | plg_twofactorauth_yubikey (3.2.0) | plg_twofactorauth_totp (3.2.0) | plg_jem_comments (2.2.0) | plg_jem_mailer (2.2.0) | plg_editors_codemirror (5.18.0) | plg_editors_tinymce (4.4.3) | plg_finder_contacts (3.0.0) | plg_finder_content (3.0.0) | plg_finder_newsfeeds (3.0.0) | plg_finder_categories (3.0.0) | plg_finder_tags (3.0.0) | plg_finder_jem (2.2.0) | plg_extension_joomla (3.0.0) |

templates discovered :: wrote:templates :: site :: protostar (1.0) | beez3 (3.1.0) | beez3-atb (3.1.0) |
templates :: admin :: isis (1.0) | hathor (3.0.0) |

i think have 2 problems on website: 1) website hacked: created file "info.php" in root, , file typically hacked file (which means it's possible has ssh access account), , 2) may have changed permissions on site may have caused login issues (or may have disabled plugins).

the easiest way fix problem revert backup , cleanup website.