Hi,
I am using photoshop since long time in MAC. But it is getting too slow I do't now what is the reason. now i got irritate i want a proper solution.
so please advice me which I should use in place of photoshop?
GIMP is a pretty decent solution and it is a freely distributed software. The majority of functionalities you find in Photoshop can be found on GIMP. You can read more about it here. - http://www.gimp.org
It's also worth keeping an eye on what Affinity are doing. They have a photo editing app in Beta at the moment, but I expect it can't be far off being production ready:
I have been using Photoshop extensively as a print and web designer over the last 10 years and I can't say I have ever had speed issues. What are you using it for? If speed is the issue I would suggest upgrading your system.