If possible, do share the docs or the guide to do it.
Is it possible to remove dnf package manager and install apt package manager in fedora?
No it is not possible. Apt is the packet manager of Debian based Distributions.
Fedora works with RPM packages and therefore it is used dnf.
If you tell us where you stuck we probably can give you some help to deal with.
Short answer: No.
Long answer: Yes, but not in a usable way.
You can remove anything from Fedora (or any distro). Removing dnf is trivial using rpm (don’t do it!). Your system should continue to work without problems… other than not being able to use dnf.
You can install
apt; it’s packaged in Fedora for development/testing purposes. Obviously if you were going to use dnf to install apt, you’d need to do it before removing dnf. You could also build apt from source.
But, packages from each distro are different: different versions of the packaged software, compiled with different versions of the compiler, different build options, different versions of dependencies/libraries, different file locations, different configuration.
Even if you install
apt on Fedora, configure it to use repos from let’s say Debian stable, and install a package, it might not work because of version mismatch or other conflicts. Very simple programs might work (e.g. a package with only a single standalone shell script), but anything more than that and you will quickly run into conflicts, overwrite files owned by rpm/dnf, and end up with an unusable system.
If you want to try it for educational purposes, use a virtual machine (VM) and don’t store anything important in it.
Even this can make you troubles if you try to display/store/change a path/file not existing in fedora.
Reading the other question, I’m beginning to suspect that there is a familiarization problem with dnf that most of us had trouble with in the beginning.
Probably, telling us which commands most are used would give us the possibility, to better help you.
dnf is a powerful great tool where you start to love as more as you use it.