'Schon fertig' means: I am already done with my work, I have already finished. As word before an adjective: Er ist schon klein, oder? He is small, isn't? Sie ist schon schön, oder? She is beautiful, isn't she? In this case the meaning is not 'already', but this modal particle used by the speaker expresses his assumption that the other will agree with him. I have no idea what 'fertig schon' could mean. I would need more context.

Schon mostly means already But it'a up to the context

Sounds strange to me. Do you have a full sentence as an example?

thank you, ann D

"Fertig schon" sounds wrong to me. Could you post the whole sentence you saw this in? You normally use this before the verb. Some correct examples would be: Ich bin schon fertig. (I have already finished.) Ich kenne das schon. (I know this already.) Ich habe schon gegessen. (I have already eaten.)