How to Remove Trojan: Win32/Kovter-Antivirus-Effective Removal Guide

Hi! A few days ago, after updating FireFox, I saw a file in my downloads labeled "firefox-patch.exe". Not suspecting anything malicious, I ran the program. It appeared to do nothing, however later I started getting lots of Windows Defender notifications about detected malware. I took a look at the Event Viewer logs, and in Windows Defender, it says that it failed to remove the virus. 215 times. I clicked on one of the detections, and it said the virus was a "Trojan: Win32/Kovter". It labeled it with the severity "Severe", and identified the file path as C:\Users\ . . . \Downloads\firefox-patch.exe. At this point I realized that I had made a detrimental mistake. I looked online for solutions, and many of them said to backup files and restore. Is there a way to remove this virus and the associated infected files without doing a backup and restore? Also I cannot do many things to the file, including compression. D: Please help.

------------------------------A help letter from a victim