Well it can’t be fixed with css code. You need to set different image proportion in the plugin itself. Check the screenshot here where I’ve indicated in which file & on which line you’ll be able to update the code: http://prntscr.com/n4f6nn
Also it seems your PHP version is outdated. Please ask your hosting provider to make it to the latest version which is 7.2 or 7.3. For the outdated version I’m unable to save any file via WordPress editor as its loading & loading but never save. You can update that file as I’ve told you to make it full instead of playbit_sponsors_thumb.
Hope this will help you.
Regards