Are vpns really private or will somebody still know you're using it and what for?

Some websites won't let you connect with a VPN, they insist on tracking everything you to do so they can make money off you. Those sites need to be avoided anyway so it is good when they block you.
Just be careful what you click on when visiting some sites.

idk i'm not an expert in tech

It just makes your ID show up in another country.

It only works if noone with tech knowledge isnt tracking you. It can be fairly easily traced back.