I need this reply for a large user base prospective, where each second too many request going to that particular contract , so the question is what is write per second limit and what is read per second limit.
There is no read/write limit on the smart contract level. The number of reads you can do a second is purely dependent on your node infrastructure, i.e. how many nodes you have and how powerful they are.
The number of transactions (write) you can send is dependent on the network. The network has been heavily congested lately, so the speed is really dependent on how much you're willing to pay per transaction