Help me fix my website

General information for the website: Hasn't launched yet
Description of every page/module: Hi,

I tried uploading a theme to my Wordpress site but it didn't work. I've deleted the theme now via FTP, but when I go on the url (sisterswhosquat.com), it still isn't working and I get this message:

"Fatal error: Uncaught Error: Call to undefined function mysql_escape_string() in /homepages/4/d549611565/htdocs/clickandbuilds/SistersWhoSquat/wp-content/themes/twentyseventeen/functions.php:60 Stack trace: #0 /homepages/4/d549611565/htdocs/clickandbuilds/SistersWhoSquat/wp-settings.php(425): include() #1 /homepages/4/d549611565/htdocs/clickandbuilds/SistersWhoSquat/wp-config.php(80): require_once('/homepages/4/d5...') #2 /homepages/4/d549611565/htdocs/clickandbuilds/SistersWhoSquat/wp-load.php(37): require_once('/homepages/4/d5...') #3 /homepages/4/d549611565/htdocs/clickandbuilds/SistersWhoSquat/wp-blog-header.php(13): require_once('/homepages/4/d5...') #4 /homepages/4/d549611565/htdocs/clickandbuilds/SistersWhoSquat/index.php(17): require('/homepages/4/d5...') #5 {main} thrown in /homepages/4/d549611565/htdocs/clickandbuilds/SistersWhoSquat/wp-content/themes/twentyseventeen/functions.php on line 60"

Please help me fix this.

Many thanks

Oli
Description of requirements/features: Help me fix it
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