I highly recommend that you familiarize yourself with Linux!
Many people start with Linux Mint, but since Mint is NOT designed for anonymity, I recommend QubesOS and Tails.
However, these operating systems require in-depth knowledge of Linux.
So start practicing!
If you can't or don't want to divest with Windows (why, what's wrong with you?) at least remove all the bloatware.
Chris Titus offers clean isos for download.
You can also find other very handy tools on his website! Have a look around!
Route your Internet traffic through the TOR-network. Either with Tor itself or by using Whonix.
If you don't want to do that (maybe because of latency), I recommend Firefox or Brave (Chromium based and with Tor implementation).
Recommendations to adjust the security and privacy settings will be added later.
If you don't want to use Tor or Whonix, you should at least use a good VPN service.
Proton and Mullvad are good addresses that you should take a look at.
There are many E-Mail provider on the web, lots of them offer free account.
Many of them say they are focusing on privacy.
But Proton perhaps is the most secure out there.
They also offer other services like VPN and Cloudstorage.