Shutter curtain only opens half way

Camera repair requires a lot more skill than most other endeavors. Sometimes there are traps which can get you during disassembly (like the AE-1 tungsten wire). I don't know this particular camera. You can probably lube and adjust curtain speeds by removing the bottom plate. The other ends of the rollers are on top, with more disassembly required, and the attendant risk. To adjust the speeds, though, you need to be able to read them. We do this with an optical device which measures the open time, and the transit times of both curtains. At speeds above 1/60, or 1/125 for metal shutters, the second curtain starts before the first curtain finishes, so there is a slit that moves across the film. This allows for exposures less than the curtain transit time, but means the two curtain speeds have to match, otherwise there is an exposure gradient. Adjusting speeds would be a challenge without the equipment. Lubrication alone might fix it, though.

I don't think you have much to lose if you're careful not cause damage. If you can't fix it you can then take it to a camera shop. Be parsimonious with lube, though. You'll want something like a watchmaker's oil, and you want to apply it with an insulin syringe, or a droplet on a needle. Too much is disastrous.