Take a look at Da Vinci Resolve.
https://www.blackmagicdesign.com/products/davinciresolve/?gclid=Cj0KCQjwnNyUBhCZARIsAI9AYlF1KJd8KPKTRtUHRr2FeftJzIzcv4kg0tOtjTf2LqLhjJ2h2kBGQOUaAsASEALw_wcB
However, if iMovie is not responding it likely is caused by something amiss in your system. Do you have enough free space on your internal drive? Have you tried booting in safe mode? Did you reset your System Management Controller. Did you try deleting preferences? Did you try opening in a new library? Did you try opening iMovie in your Guest Account?
If you've tried all of the above without success, then you might want to consider calling Apple Support. To do that click on the Get Support item in the upper right hand corner of this forum's screen and navigate to a place where you can enter your phone number. The techs there have the capability of remotely accessing your computer, that we cannot do here.
-- Rich