I know the meaning of word 'so', but I don't know how to use it properly. I see that 'so' can be a adverb ("So, I will...") or in middle (Now I'm developing an another project, so...),
but "So am I"...
Why not "So I am" ?
And how to use "so" word ?

I think you've got it. From Google (using "define: so"):

Adverb: To such a great extent: "the words tumbled out so fast that I could barely hear them".

Or

Conjunction: And for this reason; therefore: "it hurt, so I went to see a specialist".