Remove Uppercase Accents plugin

Dear support, this is the first time I am seeking for your assistance. I saw that you provide general WordPress help. I would be forever grateful if you could help me with the below.

I am using a theme that I bought from themeforest (champlacanienathenes.net). The theme supports a mega menu (first item in my header menu). When seen in mobile phone dimensions, the slide-in/sandwich menu shows all sections of the mega menu as children of the parent mega menu. The demo is here: http://webnus.co/themes/vision/forward/. All that is great.

However, my website will be translated in three languages, EN, FR and Greek. Although not a mistake, in Greek it is very ugly to see capital letters with accents. This was not foreseen by the theme, and the page titles are automatically capitalised without excluding the accents (see here: https://champlacanienathenes.net/epikoinonia/). I found a plugin that does exactly that: it removes uppercase accents for the greek language (https://wordpress.org/plugins/remove-uppercase-accents/). However, when activated it interferes with the mobile version of the mega menu. The mega menu does not open anymore in mobile version to see its children mega menu items.

Could you please help me replicate the function of the plugin by inserting some code? I saw that wordpress has this function: https://codex.wordpress.org/Function_Reference/remove_accents. However I do not where to put what code.

Many thanks in advance

Christos