Alrighty, so go into your Minecraft launcher. See the button on the bottom that says PLAY? There should be a smaller button next to it with an arrow pointing up. Click on that. That will show you all of your "profiles" or launch setups. Most likely, if you've always played the most recent version, you'll only have one setup.
So look at the top of the launcher under "MINECRAFT" and look for Launch Options (it should be next to Settings). It's more convenient to have at least one profile set to the latest release, and any others set to previous versions. So click on the button near the top that says "Add new" and give your new configuration a name and select the in-game version. As said above, there are some compatibility issues with 1.13 (your inability to chat has been discussed before on the forums! Other people have had this issue.), so I'd recommend you downgrade to a version somewhere in the 1.12 spectrum. For example, right now, I use 1.12.2 because that's the most recent version of Optifine.
Once you've picked your version, click "SAVE" and go back to the "News" screen (select that from the top) and make sure you're going to launch the right version by clicking on that upward arrow again (next to the PLAY button). You should see all of your configurations there. Just select the one you want to launch, and voila!
Send me a message if you need help with anything else or if I didn't explain this well enough.
I hope this helps!