Praying in tongues, is the 100% perfect and direct prayer to God. We can not make mistakes when we pray in tongues, but we can make mistakes, when we pray in English.
Praying in tongues, builds and strengthens our harts or spirits in the ways of God. It like building a house, brick by brick. The more we pray in tongues, the more we become aware of the spiritual things from God, and the more connected we feel with God. Praying in tongues means giving praise and thanks to God by our spirit (1 Corinthians 14:16 NIV).
I believe that praying in tongues, transforms us and makes us more like Jesus in our character, faith, love, and daily life.
It is clear in the 1 Corinthians 12:10, that to one person, are given different or various types of tongues. It says tongues, plural and various, not just one type of tongue. That means, one person can be given as a gift from the Holy Spirit, a few different tongues or languages. So one christian will be able to speak in a few different from each other tongues.
Years ago, I met a brother in Christ, who told me that he speaks 8 different tongues given to him from the Holy Spirit.