Question

in French how to say when I was younger I didn't think much about the future (in the imperfect)

Answer 1

Yasss! I love French. Oh, I need to answer. (LOL) When you write, "When I was younger, I didn't think much about the future (in the imperfect)", you write it like this: 
Quand je étais plus jeune, je ne pense pas beaucoup à propos de l'avenir.(à l'imparfait)

Answer 2

"Quand j'étais plus jeune, je pensais pas de l'avenir."

Also, instead of saying "de l'avenir", you can say "au futur"

Good luck.