I have to say, an app in the subscription that costs 50 euro per year was too expensive for me. I write absolutely free-time technical, often just fanfiction, because it is not worth it, but spend a bit of money or at least a fixed price I find absolutely okay.
Above all, it would be important for me to be able to synchronize the laptop and the mobile phone, or at least transfer it quickly or even save it on both devices simultaneously via the Internet.
It would be great if it has the features "Characters", "Ideas", "Chronicle / Script / Timeline" extra.
Please no normal writing programs such. Microsoft Word. I'm looking for an app that facilitates the planning of a story, not a pure writing app.
Take a look at wattpad. Is free, is available as a normal website and as an app. Unfortunately, there are not the features you want. But you can create these over chapters that you do not publish.