use thumnails with Related Posts Widget 123 withThumbnails

hi everybody, i try to optimize a little bit my page loading time! on articles for example here https://www.abenteurer.net/134-guatemala-reisebericht/ i want that the plugin Related Posts Widget 123 withThumbnails uses the thumbnails 85x85px and not the full size pictures!
too bad i have had disabled the thumnail generation. but plugin regenerade thumbnails helped me out! i regenerade them @85x85px but the plug dont use them!

thanks for advices!