The use of や and sentence meaning In the previous sentence, what is the purpose of the after ? I'm also unsure if the sentence is saying that **"Matsu went to the park behind the ramen shop."** or **"Matsu went to the ramen shop and the park behind it."** Thank you!

The here isn't the particle, it's , which means "shop", and is very commonly used as a suffix to words to represent places that sell exclusively, or mainly, that thing. So is the ramen store, just like is a bookstore, and is the place where you buy saizeri (actually that last one's not true).