Best way to learn
Which is better? Learning 2 other languages or 1 other language at the same time?
Just do what you want. If you have the motivation and the time you can learn as many languages simultaneously as you want. Some people can get confused if the two languages are similar (eg. French and Spanish), but that usually only happens if you're a beginner in both. So it might be wise to pick two unrelated languages, or wait until you get one up to intermediate before beginning a new one.