It was all some time ago. I seem to remember asking if THE Holy Spirit was giving you utterance in a heavenly language, why wasn't it in THE heavenly language? It was obvious that everyone had a "tongue" of his or her own. Apparently everyone was given their own heavenly tongue with which to commune with God. You didn't know what you were praying with your intellect, but your spirit did and was communicating 🙏your needs to God. Because you didn't know what you were praying, neither did Satan 👿, and he therefore couldn't interfere.
I think that's pretty well how it was all explained to me.
There was a lot of urban mythology on both sides. The deniers'* urban myth would have an expert in languages go into the church and overhear someone ordering fish and chips in old Latvian. The pro side would have a pastor praying in tongues over someone; they'd say "Do you know what you just said?" "No". "You just said 'Such and such' in Language X!"
* Mainstreamers who didn't believe in the Pentecostal version of tongues.