I moved the discussion from another user thread to your own thread, you'll have more visibility that way.
Regarding your question:
First of all you got a 7 days free trial to test things up
Photoshop 1 app only is usually £19.97 a month (I don't know your country, but prices are similar all over the world)
But you can take advantage of the "photography plan" for £9.98 per month, and you'll have Lightroom (a photo management and retouching app) for the same price. I think it's a good choice.
Also, if you happen to be a student, you'll have massive discounts to the whole suite of creative app from Adobe.
See the screenshot below:
and scroll to the end of the page to see what's on offer
if you're not a student, you can see all offers when you scroll at the very end and click on the "special offers" link.