DIY

Looking at the images you've attached, this appears to be an 8 ft wide by 6 ft tall fence. That's a good amount of weight in just the wood, and there isn't any part of the design that diagonally braces the frame, except the steel cable... which tore from its mounts.

My layman's view is that you absolutely need diagonal wood elements, which should only be installed after unloading the fence, either by removing the boards or by propping up the wheel-end so the frame returns to being squared. If the wheel interferes with this, remove it for the time being.

But I think you'd still need the steel cable, and if that has broken from its originally designed mooring, then this gate is already compromised. You may have to start over with a new Adjust-A-Gate kit or repair the current one so the cable will mount to the steel parts, rather than the wood.

I would say to rectify the diagonal supports first, before doing anything with the hinges, since if the hinges were actually the root problem, this gate would have already fallen over. That said, it seems to me that such a wide gate might have called for more substantial hinges.

The other commenter's suggestion to consider a pair of less-wide gates is also sound, if the goal is a minimal-fuss gate that will last at least a decade of additional sagging and weather.

With a gate that long you may have to attach a support wheel on the bottom. You'll always have sagging issues using wood. I tried doing a 4x8' gate for the parking area where I put my camper. Would always sag over time, even with heavy hinges and steel cable on the diagonal. Land was sloped so couldn't do a support wheel. Ended up having to do two 4' gates either side instead.

I own a company that does fences, whenever someone suggests a big gate my first reaction is always "nope". They never stay square, they're too heavy. It might be a few months if they're getting regular use, maybe a year if you're lucky, but either way I fully wash my hands of that shit. I won't warranty it and I do everything I can to discourage them.

If you're insisting on a driveway gate you need to find someone who can weld aluminum tube and make a frame with built-in hinges that'll rest on a pin. I don't know the actual name of that style of hinge, similar to a J bolt but my welder makes a huge plate for them to attach to a wall or post. Then you can cover that frame with wood, or preferably something even lighter.

I've made a 24' aluminum and vinyl gate like this that rested on a single hinge, and it worked. It was expensive, impractical, and had other issues, but gosh darn, it didn't sag.

Wood is just too heavy and not strong enough for a gate that gets used regularly, any fix you make is temporary