Theme not compatible with PHP 71.

When trying to login or access my site I received the following error messages.
Warning: Declaration of HB_Upgrader_Skin::feedback($string) should be compatible with WP_Upgrader_Skin::feedback($string, …$args) in /home4/jgardenier/public_html/wp-content/themes/HighendWP/hbframework/admin/utilities/class-install-plugins.php on line 12

Warning: Cannot modify header information – headers already sent by (output started at /home4/jgardenier/public_html/wp-content/themes/HighendWP/hbframework/admin/utilities/class-install-plugins.php:12) in /home4/jgardenier/public_html/wp-login.php on line 496

Warning: Cannot modify header information – headers already sent by (output started at /home4/jgardenier/public_html/wp-content/themes/HighendWP/hbframework/admin/utilities/class-install-plugins.php:12) in /home4/jgardenier/public_html/wp-login.php on line 512

Warning: Cannot modify header information – headers already sent by (output started at /home4/jgardenier/public_html/wp-content/themes/HighendWP/hbframework/admin/utilities/class-install-plugins.php:12) in /home4/jgardenier/public_html/wp-includes/functions.php on line 5946
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I contacted Host Gator and was informed the issue was with the them not being compatible with PHP 7.1. Host Gator reverted me to a lower version of PHP 5.6 which allows me to access my site and dashboard. However I was told in order to upgrade to the proper version of PHP the scripts on the site need to be updated.

I am at a loss as the lower PHP is less secure and affects rankings in google. Is there any way to resolve this?