Recently, I've been using linux(tried multiple distros). I'm curious about how linux works, it's architecture! Is there a book, guide, video, etc to learn about linux? By using linux, I get to know something. It would be better If I know how linux works!
Yeah, Gentoo is a good way to get your hands dirty. Reading the guide and trying to dig in deeper as to what you're doing will give you a decent understanding of Linux.
Gentoo itself is "just" a very solid distro with lots of flexibility due to being source-based (most distros just deliver the resulting binaries), so if you're the kind of person that would customize the things Gentoo exposes, Gentoo makes it easier than it would be on Debian or Arch. If not, it's an added complexity for not much benefit.
The Gentoo installation guide famously doesn't shy away from explaining what needs to be done, it isn't just a series of step-by-step instructions. For this reason it's a great way to start learning this stuff. Even if it won't explain everything completely, it will surely point at the right direction.
The standout feature of Gentoo is its configurability; you can configure portage, the package manager, to enable and disable features of a package at build time.
Say you don't have Bluetooth. You can just exclude Bluetooth from every package by setting the use flag globally:
*/* -bluetooth
it can even manage dependencies, a good example is picking pipewire over pulse.
It's also easy to package software that isn't in the official repos - here's a post where I did just that.
The community is fantastic and supportive, and you can often get a near immediate response in IRC.
Finally the documentation is excellent, especually the handbook.
Even manually installing Arch is a good way to understand the parts of a Linux system, stuff like users, package management, etc. Without heating your house all summer compiling the kernel.