Ahhh yes, security and privacy. Wanna be scared? Check out what Google knows about your for "ad personalization"
Google aims to show you relevant ads based on your interests. Use this tool to select interest categories so that the ads we show you are more related to your interests.
adssettings.google.com
Bullwinkle gave some pretty awesome advice. I'd follow it if I were you. But I also have more:
-Use decentralized services as much as possible.
-Use browsers that have your privacy in mind, such as Brave Browser.
-NEVER SAVE YOUR PASSWORDS IN THE BROWSER!
-Use a password manager that you trust, such as 1Password or RoboForm
-Use YouTube, but dont sign in. OR use a (in my opinion) better option such as Odysee.
-Use a search engine other than Google, such as DuckDuckGo or Presearch (the latter is awesome!)
-Consider using private windows more often, especially when doing business (paying bills, etc.)
-Use Tor, dont be scared.
-Use email, calendars, etc. that is NOT GOOGLE! I prefer Tutanota. But I also use Protonmail. Whatever you use, make sure it has encryption and USE IT.
-Get off social media. I know, it sucks. If you cannot turn it off for a week, you're addicted. Seek help. Seriously, social media is a major issues.
-Go though the permissions on your android device for every app. (Don't know iPhones). Remove apps or change permissions for things like games that need unnecessary permissions. An example would be: "Why does solitaire need access to my contacts?"
-Do that last one again after every app update or OS update. You'd be surprised how many turn themselves back on.
-Realize that you can do everything short of unloading all your technology, digging a hole and living there, and the "Big Tech" or Government will be still be able to see you, hear you, know you. Unfortunately, that is the world we live in these days. Don't stress it too much, you'll die of a heart attack. But do what you can to minimize the amount and frequency they get info from you.
This is a growing concern for many people. It will only get worse.
Another one I just remembered. If you use a smart phone for texting, download a messaging app called Signal. For Android users, set this to your default messaging app. For Iphone users, use Signal in place of your iOS messaging app as much as possible. It is completely encrypted and has a bunch of other security features built in.