I read the Russian research on hypthetical proto-languages and became confused as to what languages we really have examples of. Here is my quick list. I know there must be more, but do not plan to research it more. If you know where other languages fit in, then post a comment. Personally, I do not plan to learn any proto-languages in which nothing is ever known to have been written. Better to spend your time writing in category theory is my view.
Prehistoric attested languages: None (by definition, if a language is prehistoric, then,there is no historical evidence. So,it is unattested).
Sumerian, Akkadian/Eblaite, Egyptian/Elamite, Hittite/Luwian/Hattic/Hurrian, Canaanite/Hebrew, Minoan/Greek
Cham, Chinese, Korean, Mayan/Olmec, Bactrian, Sanskrit/Prakrit, Latin/Faliscan/Gaulish/Hispano-Celtic/Celtic/Galatian, Proto-Norse
Relationship to Modern languages
Egyptian:Elamite :: Arabic:Persian
Reconstructed Languages(more precisely, dead languages which have been revived): Egyptian, Greek, Hebrew
Constructed, but incomplete languages: Mathematics, Phonetics, Computer Programming and Scientific Languages
English comes from Proto-Norse, the reconstructed languages, the constructed languages and borrowings from all the other languages. It has too many words for any one person to know. That is why we have computers I guess.
The moral of the story. It is impossible to translate a word a basic as graphene into other languages, because it does not exist in them. Graphene is not graphite. So why do you keep inventing new synonyms just so others cannot understand. Likewise it is impossible to write category theory in any of them, so why do you think you understand anything.