For Dialogflow, if you are building an action for Google Assistant, you should use Dialogflow ES, as Dialogflow CX does not support Google Assistant integration.
Regarding Dialogflow’s intent limit, in Dialogflow ES, the maximum number of intents you can create and training phrases (per intent & per language) you can add is 2000.
If you need a Dialogflow ES agent with 8000 or more QA pairs that can be integrated in Google Assistant, you can consider using Knowledge Connectors.
To achieve 8000 QA pairs using knowledge connectors, you should split your QA pairs into 4 documents with 2000 pairs each as knowledge base documents only support 2000 QA pairs per document.
solved Can we make FAQ skill with over 8000 questions on dialogflow and amazon alexa?