I suggest shortening the message. If a warning message is too long, you risk users not fully reading it. You can probably reduce the second sentence to "Continue?". Or you can even completely get rid of the second sentence and use more descriptive buttons. E.g. the confirmation button can be "Clear unsaved talk details" or "Get rid of unsaved talk", and the cancel button can be "Don't erase talk details!" or "Oops, I'll go save the talk details".

I also suggest to start the first sentence with the important part. E.g. "The entered talks details will be lost." or "Unsaved talk details will be lost if you add a new talk." (I dislike that we're calling the action "adding" a talk, since it can be confused with saving a talk, but that's another issue for another time).