A common issue that can occur with users new to installing WordPress themes is a "Broken theme and/or stylesheets missing” error message being displayed when trying to upload or activate the theme. This error message does not mean that the theme you have purchased is broken, it simply means it has been uploaded incorrectly. Luckily, there is a very easy fix.

If you have download the full package you need to first extract the file you’ve downloaded from ThemeForest, the theme is inside of it along with documentation, license, and other files. You need to upload only theme folder to your WordPress. This might be helpfull:

If the import stalls and fails to respond after a few minutes, or it fails with a simple error message like “Import failed,” You are suffering from PHP configuration limits that are set too low to complete the process. You should contact your web host and ask them to increase those limits to a minimum as follows:

• max_execution_time 3600
• max_input_time 3600
• memory_limit 256M
• post_max_size 64M
• upload_max_filesize 64M
• max_input_vars 3000

You can verify your PHP configuration limits by installing a simple plugin found here. And you can also check your PHP error logs to see the exact error being returned.

After doing this you can reset your database using the WordPress Database Reset Plugin and try to re-import the demo data ( WARNING : Reset the database will make you lost all the data of your current wordpress )