GSM-Forum - Galaxy S5 clone root problem. Bootloader not working

Hello. A few daya ago I got a chinese Galaxy S5 clone, G900S (South Korean) model MT6589, Android 4.4.2 Kit Kat with Kernel 3.4.5.

Well, I was trying to root the phone which was successful. However, I tried to flash it with CWM. But it wasn't a compatible version and somehow the bootloader stopped working. When I try to access it, only black screen shows up. But the system loads normally, I haven't bricked the phone. Everything works fine, phone is rooted as well, but the bootloader is not. I think the problem is with the CWM. I guess the system triea to load it but it cannot so it's in some kind of bootloop. But when I don't try to access it, system starts normally.

So is there anyway to flash/fix/replace/restore the bootloader to make it work? Also is there anyway to access a download mode? Because this chinese version has only Factory mode with some chinese texts.

Or is there any way to stock restore the whole phone without the need of a download mode? I'm very desperate. I've been facing this problem for three days now and searched the whole internet for solution with no luck. ANY suggestions or help would be great. Thank you.