What was the first language before god split up the languages?

God did not split up languages.... language may never have been 'unified' in one first language, but there may have been separate and unconnected origins of speech and language. Many languages evolved out of other, earlier languages just as English is a blend of Latin, Germanic and old English with bits of others thrown in, and just as French, Spanish Portuguese and Italian can all trace their roots to Latin... which in turn shows connections with Greek. However there is no known link between the supposed ancestor-language of all these - proto-Indo-European.

Nor is there any known connection between proto-Indo-European and the supposed Australian aboriginal language Proto-Pama-Nyungan or the native American languages.