How do I root Lumia with Google Android as Lumia devices are very cheap but not user friendly at all?

I see that you have a lot of misconceptions, here at the first place. Before answering the question itself, let me make an attempt to clarify them.

I'm dealing with just 2 mistakes that you've made here - the most basic ones, when it comes to rooting, unfortunately.

In the first place, let's get to know what rooting actually is.

Now, installing a new OS on a device is not what rooting is. "Rooting" is a procedure used to acquire superuser permissions on an Android. The android OS is based on the Linux. In Linux, su command will give you what Windows calls "Administrator" powers. But, Linux offers much more power, to be frank. In an Android device, gaining superuser powers basically helps us "do" things that is locked away from an average user. Rooting, is a simple procedure, but once completed,leaves you with the power to tweak the complete software on the device.Sometimes, things can go awfully wrong, and that is why the Mobile manufacturer voids your device's warranty once it is rooted. Installing a new OS (now, I wouldn't call that new; it's better called a Custom OS. I'll get back to that point later) is only one of the many things that can be done after your device is rooted. Similar procedures are available on other platforms too, but they are called by different terms. Exempli gracia, Apple calls it Jail-breaking.

With that done, I'll try to explain a basic difference between an OS in a PC and that on a mobile. Let's take Windows 10 and Android 6.0, Marsh mellow for this purpose.

Windows 10 can be installed in any PC which fulfills the basic hardware requirements they ask for. Now, mobile OS do not work like that. When Google releases marsh mellow, it is not given to the end users, like Windows is. Rather it is given away to developers. To put it simply, you can't buy an installation disc of Android, like a Windows version can be. The developers still has to do a lot to make the OS compatible to their phones.  Now, that is why Samsung's version looks and behaves different from Sony's. Each model needs a different configuration, because, they differ, in configuration,features and much more. To make that even more clear, Samsung Note differs from an S6 in their OS too. Now, amateurs around the world, who make custom OS' do not make a new version of the OS. They merely tweak your phone's OS to add extra features. Why? Well the OS is designed to link software AND HARDWARE. Basically, only the developer can do that (maybe a very few ultra geniuses, too).

So, unless someone decides to make an Android version compatible to a Lumia, (in particular  to the model you own), you can't install Android on your Lumia. And guess what, the odds of such an incident is a huge zero.

Now, this is the most basic problem, in trying to install Android on Lumia. There are a gazillion ones following. And guess what, they are even more intriguing.

So, my answer to your question is:

You just can't do it.