Is disco an intransitive verb? Do we learn Latin, or do we learn about Latin? Which is correct in Latin?
Discimus de Latina.
Latin “disco”(I learn) is a 3rd conjugation transitive verb that therefore takes a direct object, i.e. an accusative case, as in “Latinam discimus linguam” literally meaning “We learn Latin language” and then “We learn Latin”.
In short, you must say the equivalent of "We learn Latin", not of "We learn about Latin".
As for “Discimus Latinam”, it is wrong as it lacks the noun “linguam” (language) which is necessary in Latin.
Similarly “Discimus de Latina” is absolutely wrong because the transitive verb “disco” takes the accusative, as I've already said, not the preposition “de” + the ablative case “Latina lingua”.
Finally note that Latin word order is different from English as Latin is an inflected language where grammatical relationships are indicated by the endings, not by the order of the words, so that we can say for example: “Latinam discimus linguam” as well as ” Linguam Latinam discimus” or “Discimus Latinam linguam”, as they all meaning “We learn Latin”, even if their word order is different.