So is this card game even playable? After starting my 3 caravans i can only play the "people"cards jack, queen, king, joker but nothing else. that happens every time I try it.

Bump of interest.

you have to press DOWN on the keyboard to change slots to place the cards.

Face cards and jokers are meant to be played against another card (going beside it) so it's playable as it's placed there by default.

If you were to play other cards you have to play them in the right slot and order. User arrow keys to navigate your cards.