Deleting Media

Hi
I need some advice on how to manage my media for some recent projects i have edited. I have imported 3 full soccer games in three or 4 files. i have since made 4 projects with this footage which i have completed. how am i best to remove the media to clear up space on my HD but allow me the capability to link the files easily at a later date so i can recall the edits.

can i just move the media to an external drive? does it need to be thunderbolt?
can i delete just the unused footage in the events from my hard drive and keep the existing footage?

in the future should i import the footage in smaller files if recording long sporting games?

Thanks in advance for any advice

Simply copy the Events and Projects to a backup drive. Then delete them from your media drive. Pretty straight forward.