Hi!
You are querying a category defined by $mts_options['mts_trending_articles_cat'], which I suppose is referring to an English category. So you need to get this category translated. As it seems that you can set it from theme options, You can create a wpml-config.xml file to get this option (and possibly others) in strings translations.
Alternatively, you can create a child theme and translate it directly in the code with pll_get_term
