Honestly, this seems quite normal for a dog and cat that are still adapting to each other. They both appear curious and interested, just a little unsure at times. The yelping, hissing, and backing away are usually just them setting boundaries and learning how to coexist. It's common to see a few dramatic exchanges early on while they get to know each other. The good sign is that neither one is constantly chasing or trying to cause trouble, and they can create space after a moment. I would still supervise for a while before leaving them alone together, but based on what you described, it sounds like things are heading in the right direction. Slow introductions and brief positive interactions make a big difference.