A level computer science nea

For my NEA I want to build a fitness program which allows you to choose workout plans or create your own one and allow you to track your nutrition such as calories and other micronutrients i.e protein, also it can help provide recipes. I've started to program the app in Xcode using swift (iOS language) however I don't know if this is the best idea would it be better to code in Html, css and Java? Would coding in swift be fine? Any advice would be great thanks.