Hello there,

1. When it comes to importing demo content, before you hit import, disable all 3rd party plugins (to free up server resources), then go to import, open chrome developer tools, hit Import, and watch console for errors. When some error occur refresh import page and repeat the process. Importing demo content must reach 100% without displaying error in the console. So repeat it until console is clear (sometimes you have to repeat process for 3-4 times or maybe more).

Please understand that this is common issue when importing demo with all theme authors since demos become more robust so they can satisfy needs of all customers, so issue is usually triggered by lower server resources. Usually it is due to low WordPress memory limit https://codex.wordpress.org/Editing_wp-config.php#Increasing_memory_allocated_to_PHP and also due to low PHP directives, so it would be good if you can increase these values or ask your hosting service to do that for you:

max_execution_time = 300;
memory_limit = 128M;
upload_max_filesize = 128M;
post_max_size = 256M;

Also, check your PHP version, it has to be between 5.6. and 7. 

Helpful reading - http://www.wpbeginner.com/wp-tutorials/how-to-increase-the-maximum-file-upload-size-in-wordpress/

2. Revolution Slider files do not import automatically, and you will need to import these slides manually.

First thing you need to make sure you've downloaded correct file from ThemeForest, from themeforest.net find the theme and in download button dropdown, select "All files & documentation".

Then you will need to navigate to Dashboard > Revolution Slider > Import and then browse the folder you've downloaded from ThemeForest and find the Theme Main Files > xml_export > revslider

Also, make sure to navigate to Dashboard > Revolution Slider > Global Settings and set these Grid Sizes that we use in our demos:

3. That is probably because the demo import you are talking about. When the demo is imported 90% sometimes the menus are missing (10% that is not imported) and you have to set your homepage in Settings > Reading. In this case, try to reinstall theme. So, check your resources, PHP version and try import once again. If you're still have troubles after doing this, please let us know!