I tried to install locally. (see the log here)
Because of my shitty internet some downloads failed. The install script doesn’t recognize that on next run. How can I recover from this and get grav up and running?
The simplest way to get grav up and running is to simply download the zip package from the downloads page here on getgrav.org.
Don’t bother trying to install from GitHub at all as you seem to be having issues with the composer installation process.
The download page has other ‘skeleton’ packages also that provide ready-to-go examples of blog/one-page/shop sites.
BTW if you really want to install with the GitHub version, you an try installing the composer vendor dependencies directly with composer update, assuming you have composer installed.