I thought after segwit activation,every thing went back to normal.
1. SegWit has not been activated yet. It's just locked in. Activation will be after this difficulty period, in (currently) 1179 blocks.
2. Even after SegWit activation, you will need to move your coins to new SegWit addresses in SegWit-enabled wallets to start making SegWit transactions.
Do any body know,exactly what fee should be set for bitcoin so that we could get our transaction confirmed soon.
There is never an exact fee.
You could look at
this site and figure out how long you expect your transaction to take to confirm with different fees. However, it's important to note that these fees are in satoshi/byte and they are
nothing to do with the fee you set overall. It's about the fee you pay
relative to the size of your transaction.
ViaBTC's transaction accelerator is still running as well, so you can use that if you have to.