Hi, Whisky (German Shepherd) is 3 months old. I take him out for a walk immediately after its meals, he does not go for toilet out, but once I bring him inside our home, he dirties the place. Can anybody tell their experience how to change its habbit

First read the housebreaking sticky at https://www.askmehelpdesk.com/dogs/i...tml#post251809 The last paragraph talks about older dogs not needing to go as soon as young puppies. His body may not be ready for a bowel movement now right after a meal. Let him take a nap. Then take him out. To make sure you catch him when he wakes up, you may want to put him in his crate. Then when he goes outside, praise him.

The earlier post in the sticky has important info in it too including the early switch to adult chow.