iMac bash shows trojan virus?

Run MalwareBytes to see if anything is found.

You can also run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper. If you give EtreCheck "Full Disk Access", then the summary of the recent logs will also be included.

Edit: Personally I would perform a clean install by first erasing the whole physical drive before installing macOS and restoring from a backup made before you had the incident. Who knows what that person did to your Mac. They could easily have compromised the security and installed a back door to get access to the Mac later on. You can either boot into Internet Recovery Mode (Command + Option + R) or by creating & booting from a macOS USB installer. Within Disk Utility you will need to click "View" and select "Show All Devices" so that the physical drive appears on the left pane of Disk Utility. Select the physical drive and erase it as GUID partition and APFS (top option). The physical drive will be named something like "Apple SSD ....".

Unfortunately, you called someone other than Brother tech support. This is a common scam where the criminals that you called will try to scare you into downloading some useless software, or in a worse case scenario, trick you into divulging your personal or financial information. Hopefully you have not provided such information.

Keep in mind that does not mean the person did not do something else to compromise your computer such as lower some security settings in order to attempt to remotely access your computer later on. It is also possible the person could have left some app behind which is unknown to MalwareBytes since it is difficult to detect brand new types of nasty apps.