Those puzzles are fun to solve, so why not give them a try? Feel free to use this post to share hints or the solution as you've found it, but please use spoilers to do so.

The first three puzzles boil down to "retro-engineering" tidbits of the the grammar of three languages (Ubyx, Alabama, N|uuki). The fourth one is to deduce the words for familiar relationship used in Arabana. The fifth one is historical linguistics, deducing the sound changes from Proto-Chamic to Phan Rang Cham and Tsat.

Check this link for the puzzles of previous years, solutions, as well as versions in other metalanguages (in case you feel more comfortable solving them in another language than English).