Shiny mew

I’ve been trying to get mew by soft resseting, but i saved the game after the “cut scene” that it spaws. Does it work or I have to save before it spawns?

You may save after the cutscene and still encounter a shiny mew via save scumming.

and how do I do that? I’ve been looking for it for a while now

Save scumming and soft resetting are the same thing.

Oh! hahah sorry.
Thank you, I will keep trying