You get an achievement every time you guess a word. You don't need to guess different words to get achievements. If you follow this guide you will guess same words a lot of times. The fastest way to 100% the game is this:
1) Start the game, select english language and the first set of words. The timer doesn't matter much but I had mine on +30 secs per word. Should look like this:











2) Guess 10 words right (they are 3 letter words) so you will most likely need to swap just 1 letter. After that the words have 4 letters each so press ESC button and then click on this button to go to main menu:











3) You should now have 10 achievements unlocked. Repeat the steps 31 times to get all achievements. Should take you around 10-15 mins, I guess.