Nouveau drivers does not refresh screen & nvidia drivers are crazy on power consumtion

Question

I want to use my laptop out doors and that is not possible because somehow the battery life is so short (2 hours at max).

1. I investigated everything possible using powertop, tlp & other unfamiliar software.
2. NVIDIA was suspicious, although I turned it off using prime-select intel it remained working (probably because it is a firmware and it is always launched). so i had to purge it. The power consumption decreased from 17-18 Watt/hour till 6 Watt/hour.
3. I decreased the power consumption further more by decreasing cpu max performance & turbo boost (setting it to 30% and noturbo to 1) (files are in /sys/devices/system/cpu/intel_pstate/no_turbo & /sys/devices/system/cpu/intel_pstate/max_perf_pct)
4. I Installed Nouveau drivers and tried to work with it but it simply does not work out of the box, not even from the live usb; when i connect the cable, both screens are on but the external screen does not refresh the frame ever, literally the mouse moves normally but to refresh the frame, i need to edit the FPS of the external monitor as in the following picture (it updates only once i change the value)
5. I inspected that installing Nouveau drivers using Ubuntu Software & Updates might be out dated so i used sudo apt install xserver-xorg-video-nouveau but instead, the external screen screen was not detected and the laptop screen turned black.