ć is short, and ci has an iiiii sound at the end. it's imposible to write the difference in any English letters, as sound ć does not exist in English. I think the best way to hear the sound is to say two words where ć/ci are at the end, like: znać and śmieci. With ć you "cut" the sound, but with ci you make it longer by saying i at the end (Polish i)
But actually the only way to know the difference is to hear it said by a Polish person.
The same with ś/si, like gaś/gasi.
But actually the only way to know the difference is to hear it said by a Polish person.
The same with ś/si, like gaś/gasi.