Actually, the question should be, “Am I pronouncing the words correctly.” Speed should be secondary after pronunciation.
For me, someone that speaks fast might be stressed, for example, a doctor. It could also be someone that doesn’t know that there are other people that speak different languages, other than English.
Someone that speaks slowly, for example, could be someone that wants you to understand an important point or emphasizes something that means a lot to them or is trying to learn English. It really depends on many factors and these are just some of them. Finding your optimal fluency (speed) in English takes patience.
Example of speaking fast would be if someone is in a hurry or is stressed about time. For example, If someone says, “Let’s go! The bus is here! The doors are almost closing hurry!” I have said this before and I didn’t have time to speak normally to the other person.
Simply put, if you’re under stress then you don’t have time to talk slowly. If you have time, then you can really explain something. However, there is something called mindfulness which is about being in the moment and actually it’s possible to slow down a little bit in times of stressful situations. For myself, I am trying to practice mindfulness and it is helping me to relax under time constraints.
One example of emphasizing something by saying details slowly and loudly, would be if you want someone to remember the color of a car, you would say, “Look, there’s a RED car, that looks just like my aunt’s.” This sentence is telling the listener that the color is the most important detail. The color RED is in capital letters to show the speaker wants you to really remember the color and nothing really else is important to them.
The person speaking fast does not mean they are smarter than you or better at conversations than you. The person speaking slow does not mean they don’t understand English or they aren’t good at having a conversation. Sometimes people need a few seconds to process what was said. The mind is a computer and also needs some computing or processing time to download what was said and then process it. Please keep in mind, especially if English isn’t their first language.