HELP

so chainsaw man was the first manga that I read..and it' just I didn't understand some parts and story, so can smone help me this

so makima was control devil and she knew about chainsaw man power from day zero and that's why she planned all this from aki to power to gun devil to just defeat him and take control of him for mankind and why every devil wanted her heart and who was reze really and quanxi really and who are those 7 arms devils and what are makima actual powers and how denji killed makima ? ahhh a lot of doubts I just didn't understand this shii