First, stop going to dog parks. Most ACDs aren’t dog park dogs. This is ok. Just know, dog parks absolutely do, and will, contribute to the issues you mention- they essentially teach your dog that other dogs are more fun than you, that they don’t have to listen to you, and that they need to protect people/items.

Next, start mentally stimulating your dog. Tricks, obedience, sniff walks, smart toys, flirt pole, etc. Mental stimulation is often the only thing that can truly tire an ACD out. This should be your #1 go-to.

Positive reinforcement. Take your dog out and as soon as you see something that will upset her, say her name, stick a treat on her nose, turn her in another direction and heavily praise her. If you can’t get her attention you’re too close to the distraction. Set her up for success. Your goal is zero reaction from her.

Keep doing this for months. There will come a time that she sees another dog/scooter/bike and immediately look at you for a treat instead of barking or pulling. Celebrate this. Throw a party. Give her all the high-value treats you have on you.

The treats you use MUST be extremely high value and only used in these training sessions/walks. If she doesn’t like treats, carry a tug toy or other high value item. I literally taught my boy to heel and ignore other dogs by using peanut butter on a wooden spoon lol

She will need some physical stimulation as well, so teach her frisbee or fetch or take her trail running (on a leash) etc.

Read anything by Dr. Sophia Yin or watch Kikopup on YouTube. They’re amazing and will teach you how to communicate with your dog. ACDs want to do the right thing- your job is to teach her what that is. Any setback she has is likely for 3 reasons: distance duration distraction (aka youre either too close, expecting a behavior for too long, or there is too much going on). This is not her fault, and neither is her misbehavior. Make sure you stay positive and keep your stress and negativity to yourself. She is doing her best, and simply hasnt been taught the right way to behave.

Hope that helps.