YOU CANNOT "MAINTAIN" A CONVERSATION
Wow, this is a nice one. I can't believe that I have not done it before!!! Clearly, you can see where I am going with this one...right?
"Mantener una conversación" is programmed into your brain so you will naturally be pulled in that direction when you speak English. "Maintaining" a conversation in English, however, is a little tricky! It's better not to use that construction at all and chose the more simplified form: "have a conversation".
For example: "It's very easy to have a conversation with him about anything".
You can use the word "maintain" in English but it's more commonly used when you are talking about a car or machine that needs to be "maintained".
Hope that helps.
Soy el director de Daniel Smith + Partners. Tengo más de 15 años de experiencia enseñando inglés a españoles.