Some people insist that the “other” tongues of Acts 2 and the “new” tongues of Mark 16 and 1 Corinthians 14 are known languages that when spoken in a church need to be translated. This denies the supernatural element of the gift of tongues.
Speaking in a “new” tongue: one not learned but received as a gift, does not make sense to the mind. But this is exactly what the Apostle Paul writes in 1 Corinthians 14:14. Naturally, there will be confusion if someone comes into a meeting and hears a tongue, and has no idea of what is being said. This is why the accompanying gift of interpretation — not translation — should follow.
By the way, when a believer is praying with his mind, he understands what he is saying. But when speaking with his spirit, he does not understand. So, even if speaking in an existing language while praying, he is not doing so naturally but supernaturally