what should the problem be?

If you have a browser window open, criminals may have embedded code in an Ad on a web site service that puts up that window.

No one can determine such stuff from outside your computer.

If you did not deliberately ask a trusted company for help with this, why would you EVER believe an "anonymous tip" that is trying to scare you into giving them access to your computer or your credit card?

If you installed Clean My Mac, use AppZapper - The uninstaller Apple forgot. to uninstall it. If that is not the case, clear the history browser on Safari and clean all the caches using a maintenance app like Onyx, then re-boot your computer.

sounds like you have the program everyone dislikes, "Clean my Mac" or something similar. Good luck on that...