GK5CN6Z laptop: Left Windows key not detected + mapping question

So I eventually decided to try to get hackintosh from my laptop: a Tongfang GK5CN6Z (also called OverPowered LP2, PCSpecalist Recoil 2, XMG Neo 15, Eluktronic Mech 15, Mechrevo Z2......), and it's almost a success.

Here are my steps:

- I went the vanilla way with Mojave 10.14.4, Clover revision 4917 and updated version of kexts we can find in this magical EFI folder found here (reddit) and there (NBR). For information, on Reddit there is also this thread and this other one speaking about Hackintosh GK5CN6Z. Success but with external mouse and keyboard during first steps.

- From here I tried to simply replace my EFI folder by the magical one in order to get "everything working" but I ended with a non booting system. I guess I shouldhave done this from the very beginning. So I undo-ed this step, then did the followings.

- Replaced VoodooI2C kexts by these custom ones to get a properly working touchpad (found in threads listed above). Success

- Followed this tiny guide to get working screen backlight control, easy as I am using last Whatevergreen version. Success

- Added ACPI folder (with patched SSDT) and OEM folder (not sure if necessary) from the magical EFI found above in order to get a working battery status. Success.

- I could make a super magical magical EFI folder from these steps in order to replace the old one that is not up to date and lack a few things (for me at least).

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The thing is: MY LEFT WINDOWS KEY IS NOT WORKING, which is annoying for many tasks. I can still use the right one (used to open the contextual menu in Windows), but not very practical. This is even stranger than that : the key worked as intended at some point during the installation process, but it doesnt anymore. It's not even detected in Karabiner EventViewer. I tried to uninstall Karabiner (finally I dont need it because I can directly use Syspref to map correct F11 and F12 keys to screen backlight), I also tried to delete /Library/Preferences/com.apple.keyboardtype.plist and reboot but it does not work (except one time where the left Windows key was working during the first seconds after reboot, but disapeared then). Can you help me find any workaround ?

IDK if it can help, but here is a strange detail to me: F11 and F12 directly work for adjusting screen backlight (as set in SysPref>Keyboard>Shortcuts>SCreen) but I need to press Fn if I want to control volume with F8-9-10.

I have one more question: I cannot find any reliable way of properly mapping my laptop keyboard. I mean I cannot find a way to get, for example, a '!' when I hit the '!' key, and so on. The only way I see is to make a complex mapping into Karabiner. So is that true ? Is there absolutely no 'easy 'way to get a windows keyboard working FULLY intuitively on a Mac ? This kind of 'custom' mapping has never been done and shared by anyone ?

Thanks for reading my very first post here :)