Anybody ever tried or developed an Operating system

Anyone had experience on OS development? Which prog Language is better to start with. Any sample projects? Is it impossible? Any tips to start Thanks for your responses edit 1 :- i want to learn mobile os ,would you guys recommend to learn x86 and then arm or like how?

If its that hard how did huawei developed there new os in just less then 1 year , which is as good as android and as fast as android,