Default and warning messages & no login

Question

a few days ago I found these default messages on my website.

Problem: I even can´t login to dashboard anymore. Some advice? This is what happened:

Warning: Declaration of Pgm_Walker::start_el(&$output, $item, $depth, $args) should be compatible with Walker_Nav_Menu::start_el(&$output, $item, $depth = 0, $args = Array, $id = 0) in /homepages/44/d407393083/htdocs/clickandbuilds/MonikaWiese/wp-content/plugins/page-menu/pagemenu.php on line 380

Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /homepages/44/d407393083/htdocs/clickandbuilds/MonikaWiese/wp-content/plugins/page-menu/pagemenu.php:380) in /homepages/44/d407393083/htdocs/clickandbuilds/MonikaWiese/wp-content/plugins/theme-tweaker-lite/theme-tweaker.php on line 100

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /homepages/44/d407393083/htdocs/clickandbuilds/MonikaWiese/wp-content/plugins/page-menu/pagemenu.php:380) in /homepages/44/d407393083/htdocs/clickandbuilds/MonikaWiese/wp-content/plugins/theme-tweaker-lite/theme-tweaker.php on line 100

Warning: Cannot modify header information - headers already sent by (output started at /homepages/44/d407393083/htdocs/clickandbuilds/MonikaWiese/wp-content/plugins/page-menu/pagemenu.php:380) in /homepages/44/d407393083/htdocs/clickandbuilds/MonikaWiese/wp-includes/pluggable.php on line 1210

Thanks!

Answer 1

Login to your C panel and in your site plugins folder, copy & cut the page-menu plugin and paste it to any other place in site directory, then refresh the site link. If it works then edit the plugin file name pagemenu.php and find the Pgm_Walker function and check the compatibility with Walker_Nav_Menu

https://codex.wordpress.org/Class_Reference/Walker_Nav_Menu