Potty Training – busy apartment + balcony

Hi! I have an 18 week old puppy and live in a large apartment complex that’s extremely busy. We spent the majority of our time indoors (besides socialization) bc he was not fully vaccinated.

We started with indoor pee pads, then turf on the balcony and now Doggie Lawn fresh grass on the balcony.

Now that he’s fully vaccinated, I’ve been trying to transition him to go potty outside.

I know he has to go when I take him outside, but every time, he insists on holding it until we’re back inside, so he can relieve himself on the balcony.

Ideally I’d love to be able to keep the balcony option for early mornings/late nights since we live on the higher floors.

Do I just continue taking my puppy out on walks so he builds his confidence and is able to relax enough to potty outside? I want him to be able to go potty in both places.

Thanks in advance for all your suggestions/advice!!