I don't really know about "onto". When do I use "onto" in the sentence? Is it different from "on" or "to"?
Answer from a Native speaker
"Onto" is different from "on" and "to." It combines the meaning of "on" and "to", "on" means something is already in position, and "to" means you are going towards it. "Onto" means to show movement into or on something. "Onto" can also mean 'in or into awareness of something'. "Onto something" means to start to discover or be aware of something. Ex: Let's get onto the boat. Ex: When the food critic told us our food was good, we knew we were onto something. Ex: I'm getting onto this new diet.