If your puzzle pieces on the playing board look too large, please change the number of pieces. The size of the pieces on the playing board depends on the difficulty. The higher the number of pieces, the smaller the pieces.
If you've already chosen a high level of difficulty, but the pieces are still large, please, turn off the zoom option.
Follow the link to learn more about it: https://androidpuzzlessupport.zendesk.com/hc/en-us/articles/209315846-How-do-I-turn-on-off-the-zoom-feature-