How can i restart Firefox Portable?

As long as it's a standard restart (not an update) and you're not doing anything non-standard (like using multiple instances, which is not recommended except on your own machine), you're usually ok with restarts. The launcher has a fallback that will wait 2 seconds and then check to see if Firefox is running if the original Firefox process it launched closes. This is done specifically to check for Firefox restarting itself after extensions are updated. I *think* quickrestart uses Firefox's own internal mechanism to restart, which restarts in under 2 seconds.