Don't paste JSON in to expressions. It's inefficient and the escaping really is a nightmare even if you do it all correct. In your screenshot, if that's all in an expression, then you have to write all the double-quotes twice in all the content, not just part of it.
By far the better approach is to import the data as a JSON project file and load it with AJAX. Then you can just paste in JSON data unmodified and you don't have to worry about escaping for Construct expressions. You only then need to escape it as the JSON spec says, which is
\" if you want to use a double-quote inside a JSON string.