@Cesarcuna The fallback action triggers if your NLU confidence is below the threshold in your config (0.3) or if none of the Core dialogue policies predict an action with confidence higher than the threshold in your config (0.3). In the examples, you gave it looks like your other dialogue policies are not predicting a next action with a confidence higher than your core_threshold, causing the fallback policy to execute.
A quick look at your stories shows me that each one of this is only includes one conversation turn. If you want users to be able to have conversations greater than one turn, I would add stories that represent those conversations. I recommend using Rasa X to collect real conversations, so you learn to handle the ways people actually talk to your assistant and include those stories. I also might checkout retrieval actions if a lot of those are FAQs