I'm a newbie and Windows user. However, I'm planning to switch to one of the Linux version that is most user friendly. Can you suggest me the best ?
You could take a look at distrowatch.com to get an overview of the many options. (see:
https://distrowatch.com/, bottom of right panel, 'Page hit ranking')
Also, wikipedia has a good graphic of the evolution of the various distros:
https://en.wikipedia.org/wiki/Linux_distribution. This will give you and inkling of what to expect from a distro from what it was based on. For example, package management (see below).
I am partial to Slackware but it's because it was the only viable one that had growth potential available to me when I first started out. At that time I was exploring minix on S-100 buses. To me, SW is the simplest of the distributions to install since the 'benevolent dictator' made it pretty much turnkey. However, saying that, moving beyond the basic install can be intimidating at first blush to new users. If you choose this distro, you WILL learn gnu/linux. There is strong camaraderie within the Slackware community (re: linuxquestions.org)
All that being said, there are distros that ease the transition from the 'trust-me' proprietary OSes like windows. PCLinuxOS purports to do just this. If you are looking for a distro with a breadth of software, the Debian and debian-like distros (ubuntu) provide an enormous software base. Not that this software can't be ported to other distros with some effort and dependency magic. If you are looking for commercial level OSes, look at IBM/Redhat or the associated community based OS Fedora and Centos distros. Arch linux and its offshoot Manjaro are strong distros with good package management and an active user base.
You may find that installing new software and package dependency management varies in each distro. From what I've seen, over the years this has been the biggest challenge to new users. If you want to trust your package management over to established programs consider APT (gnu/debian) or RPM (redhat, centos, pclinuxos). Slackware doesn't have a stock automated package dependency management. The benevolent dictator and his squires handle these dependencies by providing either pre-compiled binary packages or text listing dependencies. (see; slackpkg, sbopkg).
There so much more to explore.
As far as learning gnu/linux, it's a great time, you're entering a software candy shop.