Has the plastic dish in which najis clothes were placed before washing become najis, thereby rendering najis the clean clothes placed in it after washing, and have the bed and sofa become najis by placing najis clothes on them?

It seems the questioner is suffering from waswas (obsessive whispering/doubts), and he must ignore it. If the clothes are dry when placed in the dish, then the dish is pure and the clothes are not defiled. However, if they are wet, then there is a difference of opinion among scholars regarding the transfer of impurity, and adopting the view that impurity does not transfer is broad enough to repel waswas.