The best of Descartes’ method

In the SD
Hello Rabbi,
There was something that was not particularly clear to me, according to Descartes, in order to counter the epistemological imp, he created the ontological argument that tries to derive from the concept of the most perfect thing that it also exists, and since part of perfection also includes the attribute of infinite goodness, etc., therefore God is obliged to prevent us from thinking that is not rational. And that is the most evil thing there is.
If that’s what I wanted to ask, according to him, concepts are absolute “a priori”? After all, the elf can also change our concepts, or instill new concepts in us, so does the assumption that the greatest thing includes other concepts such as “good,” power, or existence require clarification?
And second, how was it so clear to him that good exists objectively and does not come about through socio-evolutionary development?