Problems with theme option translate

Hi I’m new in WordPress. after I built the website which is http://mediusinstitute.com/en/home-2 to make this site with 2 languages i found your plugin which is awesome, but the only problem I have is that I can’t make the translation to front page, slideshow “theme option”. All i want to translate isn’t in the settings, language, string translation, so can I add more strings by using wpml-config or by using pll_register_string? I’ve tried a lot by reading most of the posts here but i have difficulties. Please help me (my WordPress theme is schoolfun)

https://ww.wp.xz.cn/plugins/polylang/