I'm thinking of owning my first dog, and I need recommendations

I 25f lives alone. I've never had a dog before and was originally quite scared after seeing many injury-causing dogs online, but their cuteness is simply irresistible 🩷. I already have a cat, but since cats are quite independent, I want to ask about the cleaning and litter box situation, as well as safety concerns.

I'm looking for a dog that’s cuddly and adorable, yet capable of protecting me when needed. I’d appreciate recommendations on what breed, age, sex, and size might suit me best.