Good Morning and welcome. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
It is not uncommon that young puppies do not have strong anal and bladder sphincters so they cannot hold in the urine or feces. I know this is very frustrating but they do grow out of this.
In the meantime, it is better to Crate train Luna. They will not urinate or defecate in their space so place her in her crate right after her walk, feed her in the crate and make her used to it. This way, she will learn to hold in her urine and defecate when taken outside.
It will help also to purchase a DAP Collar at the pet store. This is a canine pheromone that acts as a calming agent and will decrease Luna's anxiety to help her learn to go outside.
This LINK will help.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please Reply so I can clarify for you
Sincerely, Dr. Loretta