Wow, sorry to read & see what happened, that *****. The good thing is you weren't hurt worse than you were.
As for rebuilding or repairing, I think salvaging certain parts of the structure can be done, but my guess is that you will have to rebuild most or all of it. The trusses are designed with a specific dimension of lumber & the load it supports, but the fire changed all that & the trusses are likely useless.
The studs & OSB in parts of the garage may have faired better than the trusses, you'll just have to determine that when you actually rip into things during the removal. From the looks of how badly burned some of the interior is, I'd say the temperature got pretty damn hot & damaged more than you can see.
Some of the siding may look okay, but the heat will have warped or distorted a lot more than you think. The vinyl panel may appear okay, but if it stretched or sagged just a little, it'll never lock correctly to the panel above or below, & may come loose. The same may happen for the roof & leaks won't be fun to fix later.
If the size of the garage was working for you, the foundation & floor should be fine & that can save you a lot of time & money as opposed to a new structure. Even if you need more space, adding some to the existing footprint or going upward with a second floor or loft is still lesss money than an entire new building.
Hope you can get things back on track, good luck.