I have visited your website and the fonts are displayed as they should and there is no option in Theme Settings available to optimize only the non-English characters.
Please explain what you require to achieve with the non-English characters to check it myself and help you out accordingly.
Hey, somehow my banner texts are fixed now they look okay but the problem still continues in some button links etc. Basically i want to show the letters (ş, ü, ğ, ç, ö) in harmony with others.
I saw the screenshot you attached. It seems that the non-English characters are causing issues with the font-weight that is added to the text on the product page.
Please try adding the following Custom CSS in the Global Custom CSS area under Theme Settings >> Custom CSS.