Newbie Mac user

These days, a lot of core macOS files live in a cryptographically-signed "sealed system volume". The Mac runs off read-only snapshots of this volume, making it near-impossible for malware to successfully modify that part of the operating system, let alone modify it without being detected.

There are other security mechanisms in operation, too.

Protecting against malware in macOS - Apple Support

Although it is not impossible to attack weak points in a computer's security – even a Mac's security – criminals like easy money. They figure that it is easier to "hack" you than to hack your computer. So, when receiving unsolicited messages of any kind, in any medium, you need to be on guard.

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

On a different subject, since you said that you were a "newbie Mac user", you might be interested in these Support links:

Mac - Official Apple Support

MacBook Pro and MacBook Air - Official Apple Support

Mac User Guide - Apple Support

Switched from Windows to Mac? - Apple Support

No; instead, avoid downloading software from sources other than the App Store and the developer websites.

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The idea that a third party, with no special knowledge of the inner workings of MacOS, can somehow find a simple way to protect or speed up your computer — that is not already being done by MacOS itself — suggests that the MacOS developers are somehow "holding out on you". That is absurd.

Your exceptionally well-crafted Macintosh computer does not accumulate filth that needs any third-party anything to clean it. Everything needed to run it efficiently was included in the box, except ONE: a drive on which to store a second copy of your files in case the first copy is damaged or deleted by accident. The backup software, Time Machine, is already present -- integrated deeply into MacOS.