“I need to explain this better so he understands.”

That sounds reasonable until you separate the two jobs.
Your job is to communicate clearly, honestly, and respectfully.
Their job is what happens next.

They may understand.
Disagree.
Ask questions.
Become defensive.
Misunderstand you.
Think about it differently.

Good communication can influence another person’s response.
It cannot determine it.
When you make their response the measure of how well you communicated, you can end up explaining, defending, or rewording long after you’ve already said what needed to be said.

Ask yourself: What part of this am I trying to make go a certain way?
Sometimes the next step isn’t explaining yourself better.
It’s recognizing where your part ends.