Help: Warning: in_array() expects……

I am BRAND new here, and just trying to self teach myself some WP basics and learning how to build pages, etc. Apparently, I managed to break my site, and I have no clue how to fix without completely starting over. My site is https://www.bestphotoedits.com. Not sure what triggered this, but I’m now getting multiple error messages when trying up update a page. Do you have any suggestions on how I might fix this without blowing up the site?

Warning: in_array() expects parameter 2 to be array, string given in /home4/ssolberg/public_html/wp-content/plugins/download-media-library/download-media-library-admin.php on line 74

Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at /home4/ssolberg/public_html/wp-content/plugins/download-media-library/download-media-library-admin.php:74) in /home4/ssolberg/public_html/wp-content/plugins/wp-file-upload/wordpress_file_upload.php on line 2

Warning: Cannot modify header information – headers already sent by (output started at /home4/ssolberg/public_html/wp-content/plugins/download-media-library/download-media-library-admin.php:74) in /home4/ssolberg/public_html/wp-admin/post.php on line 233

Warning: Cannot modify header information – headers already sent by (output started at /home4/ssolberg/public_html/wp-content/plugins/download-media-library/download-media-library-admin.php:74) in /home4/ssolberg/public_html/wp-includes/pluggable.php on line 1178