Advice for potential first time dog owner

I am looking for advice as a potential first time dog owner.

I have been together with my partner for 7 years and I’ve always known him as a huge dog lover. He always gets excited when he sees a dog and he’s owned several dogs in the past, which I don’t know all the breeds of, but one or two were Rottweilers. I have never owned a dog; we had a cat at home growing up.

My partner moved countries and that’s how we met and we’ve been living in a rental apartment so getting a dog was never a serious option but my partner has always talked about it.

Now, we’re moving into our first real home with a tiny backyard and all he wants is to get a puppy. We’ll be living by the beach and he can’t wait to frolic with the dog, which I can totally see and I think getting a dog is great, but here’s my issue:

When we move, I’ll be 4.5 months pregnant with our first baby. Also, we currently both work fulltime, and after the baby comes we’ll each work 4 days/week and no-one will be home 3 days/week. My partner is thinking about us getting a dog like a Toller, Aussie shepherd or Retriever. However, from what I can read online these dogs (and most dogs really) aren’t compatible with our working life schedule and we’d have to make arrangements for them for the daytime, which idk if we can manage financially with the baby on the way. Ive expressed these concerns repeatedly and my partner says he has vast experience with dogs, even in small apartments, and they will be fine staying alone from 8am to 6pm especially if they can go out to the garden, and that he’s had no issues with this in the past. To me, this seems impossible, and when I press the matter, he gets disappointed and looks so defeated thinking we’ll never have a dog (it’s still a shared decision we’re making).

I’m looking for any advice you can give me to navigate this, I want to make my partner happy and finally get a dog he’s longed for so long, but I also want to make responsible choices and not potentially mistreat a future puppy.

Edit: TLDR: partner (dog lover) and I (dog novice) want to get a dog when we move to our first house, but I’m worried about the time investment