The problem is, that the theme takes the 250x213 thumbnail pictures and upscales them to 345x213 on a lot of screens. This way, the image can’t be in good quality. You can see for yourself on www.fgreiden.ch
Okay everyone with the same problem, here’s the solution:
Please make a backup first…
Connect to your server via an ftp, go to wp-content/themes/illdy and open functions.php
Search for the line with: add_image_size( ‘illdy-front-page-latest-news’, 250, 213, true );
Change to: add_image_size( ‘illdy-front-page-latest-news’, 345, 213, true );
Go to your wordpress, force regenerate your thumbnails with the plugin. Now the picture under the news section should be in better / acceptable quality.
If it still looks a bit blurry, you could use EWWW Image Optimizer plugin and/or change the functions.php to: