Trusted number and email
In System Settings → [your name] → Sign-In & Security, check your trusted phone numbers. If you changed SIM after moving, add the new number — but keep the old one while it still works.
Recovery contact
Add someone you trust as a recovery contact: they can help you get a code if you lose access. That is more reliable than remembering security answers.
Find My and Activation Lock
With Find My on, you can see the laptop on a map and lock it if stolen. But when selling a Mac you must sign out of your Apple ID, or the new owner cannot use it. When buying a used MacBook, check this in front of the seller.
Passwords
Keep your Apple ID password in a password manager or written down at home, away from the devices. Never sign in on other people’s devices or share verification codes — not even Apple asks for them.