That's unfortunate.
The "Internal Server Error" message indicates that you had a PHP error but that error was hidden by your web server with that generic message.
So to know what is the problem, you need to look in the PHP error log of your hosting to find the fatal error message.
However, what's likely is that there isn't enough memory or execution time allowed in your php.ini to allow the install process to extract/move all the files of the install package.
I would recommend doing a FTP install:
www.hikashop.com/support/documentation/5...-to-install.html#ftp
Extract your HikaShop package in a folder called "hikashop" on your own computer.
Open your FTP software (FileZilla for example), connect to your website and upload the folder "hikashop" in the temporary folder of your website : /tmp/
Go to your Joomla Installer manager on your website backend and specify the path of your folder in the input "Install from Directory" : "\home\...\tmp\hikashop".
Click on the button "Install"... the install process should be much faster and will enable you to successfully install HikaShop.