Does Facebook spy on its users?
user
Yes, probably. Users sign up for a facebook account and understand that they are giving Facebook the right to access their information. However, its probably not clear to every user how much data they are collecting and what they are doing with it.
assistant
What can a user do to protect his privacy?
user
Privacy is complex and hard, and the answer to your question depends on what level of privacy you need.
Some general tips I can provide here:

1. Don't share your personal information anywhere above the internet.
2. Use only offline or self-hosted password manager, make your password strong (e.g., KeePassXC).
3. Delete or anonymize or pseudonymize your accounts on social medias.
4. Always use Open-Source projects (then you will know they don't spy on you).
5. Learn more about tech side (encryption, VPN, Tor).

Please, let me know if you require clarification or anything specific.
assistant