Laptop and phone use same wifi internet. Will my phone facebook get affected by porn sites from computer?

[Richard]

You should be okay unless you have a virus infection.

Do you ever open connctions between your phone and your laptop (for example, to transfer music files)? If not, see if there is a setting on the router that prevents one WiFi client from accessing another WiFi client on the same network. If you have this option and it is set, you should be 100% safe even if there is a virus floating around your network.