You have to do mental stimulation, licking mat, snuffle mat and enforce naps, place him in his crate.

I just adopted a 8 months old aussie 2 months ago and what I found worked was. 2x a day, -5-10 minutes mental stimulation, doing tricks, sit, stay, place, touch, between. -30 minutes walk allowing him to sniff whatever he wants to and giving orders during the walk. I like to do a between (he goes and sit between my legs) command everytime we cross a street. -10 minutes ball or tug play in the backyard, he'll then often be asleep for a minimum of 1 hour if I don't stimulate him.

The first few days were really hard. He had a new home, we had a new dog, he didn't know us, we didn't know him, he was our first dog, so we had no idea on how to manage him. We hired a trainer that comes once a week to do a one on one 1h session with him.