Thanks for the replies!
they raided and burned villages and cities, as well as the "Aztec books", known as the Aztec Codex. Only a few documents of these worthfull books about Aztec Culture survived the European invasion.
I must correct myself here:
The "codex"-books were from the "Maya" (these had a similar culture, but lived more to the south), not from the "Aztec"! I had been reading and watching documentaries about both Maya and Aztec and got the Codex-part mixed up...
With the remains of these "Codex" books the Maya-language and -writing is finally being translated.