Commanded to Speak in Tongues?

[KWSS1976]

When tongues were first introduced at Pentecost the onlookers understood what was being said. I have never been in a church service and understood what someone said when they were speaking in tongues...In the bible it clearly gives instructions in Corith on how to use tongues. I have a hard time finding scripture for the tongues I hear in church today cause 1. it's not the tongues at Pentecost or the onlookers would understand what was being said 2. It's not a prayer language cause I am hearing it and that goes against the Corith teaching...