How to memorize the responses said by the bot?

I am new to rasa and trying to create a bot to recommend some products based on some conditions.

At this moment, I would like to recommend the product which the users have not bought. would there be any advice to achieve this?

Just thinking whether there is a way that the bot will memorize what it has said.

For example, the conversation looks like below:

User: I would like to buy some fruits in red color.

Bot: You can go for apple, strawberry and cherry!

User: But I have got some of them already.

Bot: What fruits do you got?

User: apple and cherry

Bot: Then, let's buy some strawberries instead.

So basically, the bot can memorize what it says and then recommend the product that the users have not owned.