Erase method loadData() in Main/UI Thread because it is ASYNCHRONOUS in retrofit 2 so you don't need do it in main thread.
reference retrofit -> https://futurestud.io/blog/retrofit-synchronous-and-asynchronous-requests
and notifyDataSetChanged() the adapter in method onResponse() after you fill your result to your list.
movies.addAll(response.body().getResults());
moviesAdapter.notifyDataSetChanged();