What front end for Sq; Server

I am converting a MS Access tables and queries  to Sql Server back end. The app is a personal finance app. When completed  the back end will be cloud based. Then, I will convert the MS Access front end to cross platform(windows, Mac, Google and Linux with compatibility with Android and IOS. I don't know what language to use for this front end. I am a self taught developer and I know that I am not the best or fastest and would have to learn the language. What language would you recommend and why?