Receiving Deprecated Error after loading plugin

I keep getting this error as soon as I load the plugin to my site. This makes my site unusable and I am unable to really continue with my development. I see this plugin very highly rated and well documented and I want to use it but if I cannot get past this issue I wont be able to. Any help is appreciated.

Deprecated: Required parameter $lineno follows optional parameter $only in /home2/therefy6/public_html/wp-content/plugins/wp-rss-aggregator/vendor/twig/twig/src/Node/IncludeNode.php on line 25

Warning: Cannot modify header information - headers already sent by (output started at /home2/therefy6/public_html/wp-content/plugins/wp-rss-aggregator/vendor/twig/twig/src/Node/IncludeNode.php:25) in /home2/therefy6/public_html/wp-includes/functions.php on line 6821

Warning: Cannot modify header information - headers already sent by (output started at /home2/therefy6/public_html/wp-content/plugins/wp-rss-aggregator/vendor/twig/twig/src/Node/IncludeNode.php:25) in /home2/therefy6/public_html/wp-includes/pluggable.php on line 1355

Warning: Cannot modify header information - headers already sent by (output started at /home2/therefy6/public_html/wp-content/plugins/wp-rss-aggregator/vendor/twig/twig/src/Node/IncludeNode.php:25) in /home2/therefy6/public_html/wp-includes/pluggable.php on line 1358

Warning: Cannot modify header information - headers already sent by (output started at /home2/therefy6/public_html/wp-content/plugins/wp-rss-aggregator/vendor/twig/twig/src/Node/IncludeNode.php:25) in /home2/therefy6/public_html/wp-admin/includes/misc.php on line 1310

Warning: Cannot modify header information - headers already sent by (output started at /home2/therefy6/public_html/wp-content/plugins/wp-rss-aggregator/vendor/twig/twig/src/Node/IncludeNode.php:25) in /home2/therefy6/public_html/wp-admin/admin-header.php on line 9

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