Dropbox Sync does not start automatically?

Thanks for clarification.
However, everytime I am working a little bit closer (from a timely perspective) on more than one device, without manual syncing every change manually, I get duplicated entries and/or conflicts pretty often.

Beside Dropbox there are many other cloud services which could be used.
Are some of them more stable convenient in terms of syncing accross devices?

I assume your own one should, are there beside this other 3rd party ones which rune more smoothly?