In Judaism there is no such thing as fallen angels or conflict in heaven. Angels are messengers of G-d even ha’satan is only a prosecuting attorney in the court of heaven who only does what a legal attorney would. All angels serve at HaShems pleasure. There is no disorder in heaven.
The idea of good and evil is not about angels and demons it’s about yetzer hatov the good inclination and yetzer hara the evil inclination. We all have the potential to sin or do good. We must choose good and deal with the consequences of our choices. Instead of an imaginary conflict outside the struggle in Judaism is inside. We must use self control to control our impulses.
Angels do HaShem‘s bidding. For me all of true religion and faith first comes through Torah and then the Jewish people and the Oral Traditions. That’s how I look at things. First through the Torah, then through the lense of Jewish history. That’s how I test things.
The serpent tempted eve. And thus we have the ability to choose between good and evil, yetzer hatov and yetzer hara because of the serpent in Gan Eden. We have the ability to choose between good and evil.