Some general Network questions

Hey everyone,

i have to hold a presentation about secure networks. ive been reading about it the past couple of weeks but there are a few things which are still not entirely clear to me. i dont know how to find the answer to those questions so i hope you can help me:

• example picture: there is a strong firewall, which blocks all traffic to the internal network and only lets traffic to the dmz pass to protect devices inside the internal network. But then how do people surf the internet inside the internal network? the fw should block almost anything targeting devices in the internal network..does the router remember that i sent a request to reddit.com so the fw knows that it is a response from reddit and lets it pass?

• lets say i have a fileserver(very important data) inside the internal network and a webserver in the dmz. the webserver needs to access the fileserver though. in this case, i should set the firewall between them to "forbid all traffic from outside to the fileserver except from the webserver" right?

• if i have additional users in the internal network together with the fileserver and i dont want the users to be able to access the fileserver: is it more common to put the users and the fileserver in different vlans or to add an additional firewall in front of the fileserver?

Any help is appreciated! Thank you in advance! :)