Does Windows Defender protect me against hackers/spying?

Use Malwarebytes along with Windows Security.

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The best security sits between the chair and the keyboard.  Watch what and where you click.  If you do not know what is there do not click on "Click here".  If you get an email that sates it is from your provider look at the address of the sender.  If it has a couple of letters at the end they are probably the foreign country and that is not where your provider is located.  When downloading programs do it from the maker not anyone else and do not allow any extra items to be included.

Hi Dairy. I'm Greg, an installation specialist, 10 years awarded Windows MVP, and Volunteer Moderator, here to help you.

Windows Defender gives best Windows performance, adequate protection, is built in, has least issues and is from Microsoft who knows how to protect their OS best.

I would also run periodic scans with Malwarebyes from https://www.malwarebytes.com/mwb-download/, choosing to include rootkits in Scan Settings, so you have the best on-demand scanner in addition.

If you get infected then you can add MBAM real-time protection, until then turn it off in Account Settings.

Hacking is another issue.  See here how to protect against hacking:

Have I Been Hacked? How to Find Out and Protect Yourself - The Missing Report

How to tell if your PC has been hacked | Windows Central

12 signs you've been hacked -- and how to fight back | CSO Online Compromised Microsoft Account Help | Hacked Microsoft Account Help 

I hope this helps. Feel free to ask back any questions and keep me posted. If you'll wait to rate whether my post resolved your problem, I will keep working with you until it's resolved.

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An antivirus application - any antivirus application - can only provide partial protection against hacking and spying. We are the first line of defense.  You need to be continuously vigilant. Don't rely on software to do it all for you.

As for which antivirus application to use: Do you really think you're going to get an objective answer in a forum sponsored by Microsoft?

It is very good, but it is *not* perfect. No security software is perfect.

Yes, run Defender, and to get closer to perfection, you should  also download, install, and run the free MalwareBytes AntiMalware, and most important, practice safe hex.