How can I change fields/sections structure locally while having a live site and then upload the new structure, without wiping the production site? In Wordpress ACF you can just Sync the fields structure, here it seems I need to close down the website for development?!
There are lots of similar questions with good discussion on this:
Ultimately, we want to building something in core to help manage this and the upcoming Craft 3 has taken a step in that direction with Content Migrations.
You may find Sprout's Import plugin useful in this regard.
Take a look at The Architect plugin. This allows you to export selected attributes (e.g. fields, field layouts, sections, entry types, asset sources, transforms, globals, users and user groups) as a JSON file and import them into another site/environment.
It works very well for exactly the use case you describe: migrating the changes in content structure, not content, between environments.