Post installation issues Ubuntu 18.04-Dell inspiron 7559

The aforementioned laptop bears a NVIDIA card which has made things very difficult when it comes to installing almost any linux distro (except Mint).

I managed to install Ubuntu 18.04 but in Legacy mode which makes the initial booting to take more time than the UEFI booting.

When I switch to from Legacy to UEFI, the Ubuntu do not even boot. Does anyone know how to solve this issue?

I have already downloaded the drivers for the NVDIA, and I have done all the steps up to "installing NVDIA drivers" from this site: https://connorkuehl.github.io/dell-inspiron-7559-linux-guide/

but with the difference that in the beginning (prior to installation) I didn't do the:
"nomodeset i915_bpo.nomodeset=1 quiet splash".

I have no idea how to proceed and I am somewhat annoyed by the fact that it takes 1.5 mins to boot the OS.

Any help?

Thanks in advance

inxi output

Graphics: Card-1: Intel HD Graphics 530 

          Card-2: NVIDIA GM107M [GeForce GTX 960M] 
          Display Server: x11 (X.Org 1.19.6 ) drivers: modesetting,nvidia (unloaded: fbdev,vesa,nouveau) 
          Resolution: 1920x1080@60.02hz 
          OpenGL: renderer: Mesa DRI Intel HD Graphics 530 (Skylake GT2)
          version: 4.5 Mesa 18.0.5