Toilet train is not easy.
Its ok if he doesnt speak yet, but at least you can tell him "Before you wanna pee you tell me shi shi ok" can use baby language.
For mine, i took him to toilet every 2 hours at first,becoz tats about the timing for them to pee, and also train him to tell me when he wanna shi shi, . At 1st there will be accidents - like hiding in the bedroom to pee etc...scared to be found out...but after a while it should work fine.
But after a while it becomes a habit - pee every 2 hours. I heard that at childcare centres they also train this way.