when I use dialogflow + google assistant, I usually save a temporary data with conv.data and save to user storage with conv.user.storage in webhook cloud function javascript
but, when I use dialogflow + telegram, I didn't find that. so I want to save a score in quiz, so in 10 question, the system able to store like a temporary storage to save the score and calculate after the quiz is finish
Both conv.data and conv.user.storage are Actions on Google concepts, so are only available with that integration.
The rough equivalent of conv.data would be to have a Context with a long lifespan. Your webhook would save the data you're interested in preserving for the session in this context and then retrieve it in a later webhook call.
This is only maintained for a session, however. Any longer-term storage would require you to have a unique identifier for the user which you can use as a key into a database or data store you maintain.