Hi,
We have just checked your site and see your server is too weak.
We tried both import automatically & manually but still got 500 error when import demo data.
So please change more value for PHP settings of your server. (You can x2 value)
Then go to Theme Options -> Demo Importer to import demo.
You also can try install Local Server to check import demo:
Home
Then you can move to your server by use this plugin:
Duplicator – WordPress Migration Plugin
Hope this helps!
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Regards,
HaruTheme