Let your pup be a pup. The outside world is exciting to him. What you're expecting is like taking a 5 year old kid to the playground and then asking him to sit there quietly and do his homework.
Take the fun out of training and in 7 months you'll have an 80 lb Shepherd blow off all your commands.
Disagree. The younger the better to start imprinting and building up a solid foundation for OB. Letting the pup be a pup is what leads to an adult GSD that has no boundaries, manners, or focus as the world is more fun than their handler. Training should absolutely be fun and playing with the handler in different environments is the reward.
OP, search michael ellis engagement on youtube for some helpful videos and advice.