With all due respect, the issue is not whether Genesis is “right” or “wrong”, but rather the manner in which it should be read. Genesis 1 is meant to teach one thing and one thing only: That God created everything out of nothing, that he created man in his own image, that man seperated himself from God through disobedience, and that God immediately set about the long - or at least it seems long to us - process of healing that rift, a process which culminated with the death and resurrection of Christ. That is ALL it teaches.
Everything in Genesis is meant to convey that truth, but it is done in the ancient Semitic style of writing, using allegories, fantastic imagery, and all based on traditions that were handed down for centuries. I do not believe there was a serpent, or a tree, or a garden, etc. These are all images & allegories, in a certain style of writing, meant to convey the fundamental truth I stated above. This does not mean it isn’t true, but rather a matter of what truth is being conveyed.
So, how long did creation take? Perhaps millions of years. The two extremes to avoid are the rejection of religion in favor of science, and the rejection of good science in favor of a literal 6-day read of creation.