Xiaomi mi notebook air bios boot up using external gpu not available?!

Im quite a noob with computers and stuff but i have some seriously basic knowledge . I have a xiaomi notebook ai i5-8250U model . Im trying to get myself an external gpu setup (i know i should get a desktop but i seriously cannot afford and i want to play a few games on my laptop)

So the problem is when i got to the bios of this laptop the choices are so limited and i cannot change the ‘boot’ to disable the GPU and make the laptop use the GPU which is connected through the m2 PCIE externally. i was thinking maybe to somehow use windows 10 and ‘Turn off’ the gpu manually and make the laptop use the GPU which is connected externally through the PCIE. But my idea might be completely useless as it probably HAS to be booted up through the bios…

Thanks in advance and i would appreciate any help that would enable for me to do this/answers if its even possible to do. (i have not ordered anything yet im just doing my research to see if its possible on this laptop.)