boot - Ubuntu only booting in discrete graphics mode (GTX 1070)

I have installed Ubuntu several times on my old notebook and everything always worked fine. Now I have a new one:

• Schenker H507 (CLEVO P65-67RSRP) with G-Sync Display


• Intel Core i7 6700HQ


• Intel HD 530


• NVIDIA GTX 1070


• Crucial Balistix Sport 32GB DDR4 2400Mhz RAM

On this Notebook I have a SAMSUNG 960 Pro SSD with Windows 10 running in UEFI mode.
Now I wanted to install Ubuntu Desktop 16.04.1 LTS on my second SSD (SAMSUNG 850 Pro).

My Problem is that only if I turn on Discrete Mode in BIOS, which is for exclusively using the NVIDIA GTX 1070 graphics and shutting off Intel HD 530, I can boot into Ubuntu and install it.

Here is a picture taken after installation in UEFI mode with only discrete graphics activated.

I already tried many several solutions provided on Ask Ubuntu, but they all did not work for me. With HD 530 activated either I got a black screen or stuck at loading screen or a flickering screen.

I can install Ubuntu in Legacy Mode with both graphics cards activated, but I can not convert Ubuntu Legacy into UEFI mode.

lshw output of display in Legacy Mode:

*-display UNCLAIMED
                description: VGA compatible controller
                product: NVIDIA Corporation
                vendor: NVIDIA Corporation
                physical id: 0
                bus info: pci@0000:01:00.0
                version: a1
                width: 64 bits
                clock: 33MHz

                capabilities: vga_controller bus_master cap_list
                configuration: latency=0
                resources: memory:db000000-dbffffff memory:90000000-9fffffff memory:a0000000-a1ffffff ioport:e000(size=128) memory:dc000000-dc07ffff

*-display
             description: VGA compatible controller
             product: Intel Corporation
             vendor: Intel Corporation
             physical id: 2
             bus info: pci@0000:00:02.0

             version: 06
             width: 64 bits
             clock: 33MHz
             capabilities: vga_controller bus_master cap_list rom
             configuration: driver=i915_bpo latency=0
             resources: iomemory:2f0-2ef irq:127 memory:2ffe000000-2ffeffffff memory:80000000-8fffffff ioport:f000(size=64)

Can someone help me please? I also tried Ubuntu 16.10. Currently I have Ubuntu installed in UEFI mode with only GTX 1070 activated. I do not want to turn off HD 530 every time I boot Ubuntu.