The web app has a send-message feature. You can click on someone's name (or via searching) to go to the profile to send a message by clicking the mail-button.
You can add friends too, to be able to find then quickly to message.
Messages will go into you web app's notification (top right mail icon)
Additionally, if you're looking for even more community, check out our Discord (under Community in the menu). It's a really friendly group of language learners!