Thank you for your comments! I think I understand what you mean Georges. In my opinion the problem is how much people articulate while speaking fast. In particular I am referring to the last syllable. That's when some syllables might not be heard clearly. Sometimes, this tendency can come from the regional dialect too. But, as you said, with time and practice it will become easier.
I'm happy to articulate a bit more if I know that otherwise I might not be understood. And if I do want to use a specific regional term, I will explain it so everyone in the conversation can understand. But I guess it's a personal choice. In other words, I don't mind adapting the way I speak.
When I learn other languages, I find these differences between informal and formal use of the language interesting. I tend to "follow the rule" but also be aware of informal/regional variations of the language while listening.
I remember that, in school, I was taught that "Salut" in French could only be used when greeting someone and not when saying goodbye. I do recall my teacher insisting on this point. Well, when I moved to France I realised that it wasn't the case. I was quite surprised! This example is not really to the point, but I hope you understand what I mean.