When we invoke a God or Goddess, do they know exactly why we invoke them?

Should we tell them why we are invoking them and what we need help with?

How many minutes should this take? For example, if I have to talk for 10-15 minutes, if I have to explain myself, is that okay?

You should only invoke a god/dess if you have a strong relationship with them. Invoking a god/dess is a very high level of connection and relationship between the two.

Invoking a god/dess usually to gain knowledge, or to clean, empower certain powers. You can also use their energy to balance out your elements, but as I said this is advanced thing to do, one probably have balanced their elements out before this level of advancement and relationship.