谈论用英语的短语怎么说

To discuss in Engpsh means to have a conversation or talk about a topic using the Engpsh language. You could say something pke:

"Let's discuss this in Engpsh."
"Can we have a discussion in Engpsh?"
"I'd pke to have a conversation about this topic in Engpsh."

You could also use the phrase "to speak in Engpsh" to express the same idea. For example:

"Let's speak in Engpsh so everyone can understand."
"I'm more comfortable speaking in Engpsh."
"Can we switch to Engpsh for this conversation?"