Help - Samsung NP530U3C Ultrabook

I recently got this ultrabook that had Win10 on it and I wanted to install lubuntu to help battery last longer. the first time i tried to install lubuntu on the machine was by selecting the default option of the installer which installed the distro entirely on the 500GB drive. In this way i succeded on booting the machine but then i decided to store personal files on the 500GB hard disk while placing bootloader and such on the 24 GB iSSD. I reinstalled lubuntu. Once the installation finished i tried to reboot the machine and wasn't able to get to the operating system. I got in a loop between the samsung logo screen and the boot menu consisting of only one entry: ubuntu. I can't access the bios anymore. I tried the method listed in this forum consisting of creating a DOS-bootable stick with a bios rom on it to try and reflash it but with no success. I tried removing the hard drive, resetting the CMOS by unplugging and plugging tha battery back and also tried the RTC reset to try force the boot from usb but all with no success. The last update of today is that now i don't see the ubuntu entry on the main menu anymore and this happened after removing the laptop battery. What is still left to try? Thanks in advance.

 

you can't do the bootloader on the iSSD. if W10 is still on the main drive load up a bootable repair disk and go to command prompt. there do a /fixmbr

https://www.lifewire.com/fixboot-command-2625886

https://www.lifewire.com/fixmbr-command-2625887

 

So here's a quick update: i created a WinPE bootable usb to reset BIOS to default settings and then i fresh installed Win7. The only problem is that now the system is not able to properly boot the OS.
The only exeption is that i can get to Windows if i put a live usb on: at the message "press any key to boot from usb" i simply wait for the timeout and then windows starts loading correctly.... is it still a bootloader problem? in this case what do i have to do?