"Get in good shape" means you are going to start being healthy and go to the gym and such. I have never heard the term "Get good shape." I mean I guess it makes sense that you want your body shape to be good. What American English speakers usually say is just "Get in shape."

"get good shape" isn't a phrase that we use in english as far as i know. We either say "Get in good shape" or just "Get in shape" and that means to get healthy and/or exercise.

Get good shape 語法錯了. Get a good shape 还可以說得通, 意思是 "拿个好型狀"