What is the meaning " so" and " such ", And when and how to use so and such?
for exemple : they're so difficult to play,
it was such an interesting trip

Question

What is the meaning " so" and " such ",  And when and how to use so and such?
for exemple : they're so difficult to play,
it was such an interesting trip

Answer

'So' qualifies an adjective: so many people/ so much money/ It's so big/ I'm so tired/ They're so expensive

'Such' qualifies a noun: such a lot of money/ It's been such a long time/ It was such a good film

Answer

So / such are adverbial part. 1.So + adv/ adj that 
Example= they are singing so terrific that the audiences are  exited
So skillfuly that/ so easy that
2. So + much/ many/ few/ little + noun
She has so much money that they envy her
Such + n + that
N means all parts relating that as adjective, numerals, relative clauses, appositives 
Example= They were such two impolite foreigner learners who learn Persian that he doesn't teach them