Is MacBook Pro (probably mid 2012) second hand worth buying in 2018? Dilemma

How complicated is the graphics? Poster sized? Should go fine; but i3 and i5 is just the product line name, specific model, but we can guess a Macbook from 2012 is not good either since it had to be old gen i5 that what you have now probably eclipsed it.

2012 is just too old, check out 2013 to begin with. I do suggest PC so you don't sunk loads of money only to see obsolete hardware is not enough.

I'd bet your laptop is running out of RAM. Watch the RAM load in Task Manager, if it's maxing out then you can usually get more RAM for pretty cheap.

For Photoshop you want a fast CPU, and the easy way to compare CPUs is with a page like this:

Like Andy said, saying i3 or i5 is like saying your upgrading from a Dodge to a Honda, it doesn't really mean much speed wise. You have to look at the specific CPU model to tell if it's faster or slower.

I'd look into a newer Macbook Pro. Make sure it has an i5 or i7 processor, a large HD (and/or SSD), and minimally 8 GB of RAM, preferable 16. You might want to check out PowerMax.com. They often have really good used/refurbished Macs of all sorts, and they are great to deal with: you can actually talk to a real live person.

"Is MacBook Pro (probably mid 2012) second hand worth buying in 2018? Wondering whether I should get a macbook pro second hand which has i5 processor, 8gb ram and etc."

That "etc." has me all balled up. I will assume that all the "etc." bits are not important top you.

Buy a new 13-inch (tiny screen) MacBook Pro for $1299.

Whazat? Can't get together $1299? Then buy a Mid 2012 13-inch (tiny screen) MacBook Pro for $539, link below.

What is "worth buying" is what you can afford. If you buy nothing, you keep using the Lenovo Ideapad that is stuttering for reasons that remain unknown.