roof trusses?

hello i need to replace my garage roof currently a flat one iwould ideally like to put an apex roof on my garage is 18foot long x 9foot 6ins wide, i have been offered some trusses cheap but these are 5.9m wide x 1.77m high would it be possible to cut down these trusses and make them fit my garage and how difficult wold it be appreciate any guidance thanks gary.