VPNs encrypt your traffic and hide your IP address from your Internet Service Provider.
A VPN does not make you anonymous online. It shifts who can see your traffic — from your ISP and local network to the VPN provider. If you are logged into Google or Facebook, those services still know exactly who you are and what you are doing regardless of VPN status.
The legitimate uses for a VPN are well defined: protecting your traffic on public WiFi (hiding it from other users on the same network), accessing geo-restricted content (services that limit availability by country), and connecting securely to a workplace network when working remotely.
Free VPNs are a significant risk. Running VPN infrastructure costs money. When a VPN is free, the service is often funded by selling your browsing data to advertisers or data brokers — exactly what you were trying to avoid. Reputable paid VPNs with a verified no-logs policy are the safer choice.
VPN speed and reliability matter for everyday use. A VPN routes your traffic through an additional server, adding latency. Choosing a server geographically close to you and selecting a provider with good infrastructure reduces the performance impact to an acceptable level for most tasks.