Malicious detection at Aqua/fuctions.php

Dear,
Google Ads detect that our website contain malware with link:
- https://cobalten.com
- https://go.onclasrv.com
So, when we check website by using Wordfence Plugin show that: Aqua/functions.php contain backlink injection and malicious activity. Scanning information as below:
Filename: wp-content/themes/Aqua/functions.php
File Type: Not a core, theme, or plugin file from wordpress.org.
Details: This file appears to be installed or modified by a hacker to perform malicious activity. If you know about this file you can choose to ignore it to exclude it from future scans. The text we found in this file that matches a known malicious file is: $div_code_name=”wp_vcd”;. The infection type is: Backdoor used for backlink injection and other malicious activity..
Please support me to clear Aqua/functions.php.
My website here: https://tktg.vn