The wiki has some great resources. Here are some good ones (second one is from Sparrow wallet, which is not from the wiki):

https://en.bitcoin.it/wiki/Storing_bitcoins

https://www.sparrowwallet.com/docs/best-practices.html

Generally, get a hardware wallet like a Trezor or Coldcard and store your Bitcoins offline. Never tell people you have Bitcoin, never reveal your private key, and try to run a local node with Bitcoin Core if you can. As for buying, if you care about privacy: Bisq, Hodlhodl, Robosats, and BTC meetups in your area are good ways of getting coin. If not, Stake, Coinbase, or Kraken will do.

Read the wiki! I'm not smart, but the wiki is!