I personally don’t recommend using bells, where your dog needs to ring it to signal that they need a bathroom break. In general, it’s better that your pup practices waiting for things to happen/be started by you, as opposed to him learning that he needs to prompt or budge you for something to happen.
A smart dog will quickly learn that (even without a bell system in place) if you don’t make sure to provide things when needed, but before being asked.
Smart dogs can also even practice using the bell as a way to just get your attention and be outside without the need to pee (which can then also hinder the association), in which case, it’s also recommended that they get all the attention and enrichment outlets they need before they have to ask for it.
Have you tried logging the amount of time between pees? How long can he handle vs how much time between bathroom breaks? Figure out what his bladder can handle and take him out accordingly to that, before he even realizes that he needs to go out.
Once you have that down, you can start increasing the amount of time between bathroom breaks slowly. I do, however, recommend using a catbell with your pup! Here's how and why.