With English not being your first language, I think you can apply this plan to formulating your responses in general. Just take a moment, plan your reply, and say it. It doesn't feel that long to the other party, I promise.
Regarding flow, when asked specific questions about things, I remember the acronym CAR - Context, Action, Result. I form my answers in this framework to make a plan for how to get to the reply. Give a little context to set the stage/problem, say what you did, then say how it went - good or bad. Be concise. Fewer words get the job done and are easier on you.
Not sure that is what you're looking for regarding practical resources, but I hope it helps. It has helped me a lot, I think.