The words are only at the beginning and at the end, you can go through the beginning randomly, then there is almost no text and you will be able to evaluate the game)

Cool game! But I think we should make the screen a little smaller, because it's a little inconvenient to play(you can't see the whole map).

About the download - sometimes the download is quite long(up to 5 minutes or more). About Greenfoot - you can study it yourself(in the help tab there is A greenfoot Library tab - there are all the commands and their description, perhaps I will download your game and make some kind of algorithm that should help you.

In order to check the check, you just need to see if the pieces of the opposite team can resemble the king's cage. To check the checkmate, you need to check the check + check the neighboring cells ( if they have a shape, you do not need to check them. With a check on the cover of figures and other things will be more difficult, you can just do this, if a person(when his king is under the Mat) does not go for 20-30 seconds, so he loses + it is necessary to do so that the king could not be killed, but already, I think, quite simple.