Can I see online what is the total amount present in my NI fund?
No.
And how much my employer is contributing in it?
The employer's contribution is 12.8% (I think) above the threshold.
I wanted to know what will happen to my NI contributions, at the time when my contract gets over
I guess it will just remain in the system. It might give you some future right to a UK pension if you came back, but don't quote me on that.
Can I claim my NI fund at that time?
No. Whilst NIC affects the amount of pension that a person might receive, other than that it isn't "their" NI fund. If you are paid under PAYE in the UK and liable to NICs, you pay. Simple as that.