If your dog shows guarding behaviours, leave them well alone when they are enjoying food or playing with toys by themselves.
Always swap the dog's item for something else, being consistent and always swapping items will help dogs learn to share without being worried.
If you need to take something from your dog, swap it for something else that your dog considers to be equally or even more valuable.
You could drop several treats on the ground near your dog, so they have to leave the item to go and eat them.
Then you can calmly pick up the item while they’re enjoying themselves.
Teach your dog to swap and drop, when your dog is playing with a toy, get something they like even better.
Offer this to your dog a little distance away from what they already have, your dog should be enticed to drop what they have and come to get the new item.
You can then pick up the original item, where you can during training sessions, return your dog’s first item to them soon after you have swapped it.
This will help them to learn that letting go of something they love can be a positive experience.
Once your dog has the hang of this, you can add a cue word ‘drop’, over time, your dog should associate the word ‘drop’ with letting go of their toy, and you can ask them to ‘drop’ what they have in exchange for a tasty treat.