If yes, then how can the mass of received HTTP data routed to the
correct cellphone? And how can websites differentiate between
That's what NAT does
To elaborate, NAT uses the same IP but different port numbers for each phone.
A program using the internet must specify an IP address and a port number it is sending to.
A website will see users coming from one IP but many port numbers (there are 65536 possible ports). When NAT gets a reply back from the server, it maps the port number back to the inside, fake IP address it gave each phone.
Servers have to use standardized port numbers like 80 for a web server, so clients know how to find them, but clients can use any port number. That is also how multiple programs on a computer all use the same IP. (Such as IE and Firefox running at the same time connected to the same website.)
Since servers need standardized port numbers, it is a problem for a computer on a NAT network to be a server.
On a Windows PC type netstat into a DOS window to see the port numbers your programs are using.