I see. This is the best advice I find for those who have similar issues with their Google Account:
https://www.quora.com/An-unknown-device-got-con...
https://support.google.com/accounts/thread/1426...
However if you need further guided help I'd contact Google forums at the last link above, as this is Microsoft which is a completely different company.
If you're concerned about hacking here is how to tell and prevent it:
https://preyproject.com/blog/en/have-i-been-hac...
https://www.windowscentral.com/signs-pc-hacked
When I'm asked how to remember a long, strong password, I suggest a childhood street address + phone number you remember.
I hope this helps. Based on what you report back I can answer any questions and may have other steps to perform. If you'll wait to rate whether my post was helpful, I will keep working with you until it's resolved.
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