Exodus 1

There is a lot of Exodus that I don’t understand like why were there 10 plagues and God knew they would never be let go until the death of their first born. And why was Moses punished by not getting to go into the promise land when he had to deal with everything the people did for 40 years and he did something God didn’t tell him to do and he was forbidden from going? A lot I don’t understand in Exodus and the other books written by Moses?