I have never used an e-collar, so I cant give you any advice on that.
But, your pup is young, and I remember 8-9 month mark was one of the hardest for Kelso and us, he was stubborn (well he still is) but just really stubborn at that time.
The only thing that helped was amping up exercise and training. If your pup listens inside, but not outside it is probably because outside is fun and exciting and he has better things to do than listen to you
Our gal loves to chase squirrels and bark at the fence when outside, so to help make her come when called I had to be more fun. I kept treats in my pockets and a chuckit. Whenever I said here, they get a treat for coming here. When we have a ball everytime they retrieve it I say "here" to reinforce them coming. If one of them decides not to, I walk to the door....then they realize I am leaving and they say "hey' dont go!
Another thing you can do is keep a long line on your pup to reinforce the command.
It can be frustrating, But puppies (even at 9 months) are fun, and the more fun we are, the more they listen
What have you tried so far?
ETA: we have a fence in our yard, not sure if you do as well? But make sure you have a long line on if you do not have a fence!
But, your pup is young, and I remember 8-9 month mark was one of the hardest for Kelso and us, he was stubborn (well he still is) but just really stubborn at that time.
The only thing that helped was amping up exercise and training. If your pup listens inside, but not outside it is probably because outside is fun and exciting and he has better things to do than listen to you

Our gal loves to chase squirrels and bark at the fence when outside, so to help make her come when called I had to be more fun. I kept treats in my pockets and a chuckit. Whenever I said here, they get a treat for coming here. When we have a ball everytime they retrieve it I say "here" to reinforce them coming. If one of them decides not to, I walk to the door....then they realize I am leaving and they say "hey' dont go!
Another thing you can do is keep a long line on your pup to reinforce the command.
It can be frustrating, But puppies (even at 9 months) are fun, and the more fun we are, the more they listen

What have you tried so far?
ETA: we have a fence in our yard, not sure if you do as well? But make sure you have a long line on if you do not have a fence!