Using two languages at the same time is nothing. It’s not uncommon for programmers to use several different languages every day. Different tasks and different technologies require different languages.

Just today, I’ve already used four or five different languages, and that’s interesting because I haven’d done any programming so far. All I’ve done is work on a presentation.

As a good programmer it’s essentially required that you know your way around in several languages, and the only way of attaining (and then preserving) reasonable fluency is by using those languages.