Anyone know a good resource when it comes to explaining or sharing your thoughts fluidly and simplistically?

I've developed the habit of when I talk to some one or explain something online it's absurdly complex... like writing a book for something that doesn't need such a lengthy response. Mainly because when I did attempt to be simple or straightforward I come off overly blunt or even rude and it doesn't really get my point across.

Face to face conversations are the worst for me. I have to spend so much time thinking and being silent that the other person thinks im zoning out or stupid. When actually Im spending time and energy figuring out how to explain something. Its like Im trying to think of every possible aspect rather than respond with something simple and then have to go back and forth because its really hard for me because I can rarely respond immediately or fluidly.

So yeah... I don't know if its just as issue of overthinking, confidence in speaking, lack of vocabulary or what. Anyone got any ideas?