I bought one amount of TRK. how I get 200% interest
Just wait until the coins in your wallet are over 9 days old then keep the wallet online as much as possible, it will start producing new coins eventually
If i save 8000 TRK in my wallet, how much profit will i get in one month?
Up to 1300 TRK. It depends on many factors, can't be calculated.
I saw in the OP, there is a block POS reward limit of 200 TRK.