If you want to learn a new language, then pick a project that has a known (to you) scope, like porting an existing application you wrote. If you want to comple

If you want to learn a new language, then pick a project that has a known (to you) scope, like porting an existing application you wrote. If you want to complete a new project, stick to what you know. Risk multiples. If you want to pick a backend language, then pick one of: Go/Ruby (On Rails)/Python/node.js/PHP. If you don't know which, then pick one of them randomly. Those languages were used to ship tens of thousand web applications. Anything outside of that is an adventure. Remember: risk multiplies. Kotlin is a fine language and you'll probably be fine but I would still pick Go/Ruby/Python/node.js/PHP.