Want to know About theta

F&O
1

If I buy Nifty at strike price 1000CE and theta showed it’s value -3.08
My question is
If all Greeks are not changed what will be my premium for next day?
Total 75 ×(-3.08) = -231 will be reduced from my total value of option?

2

theoretically yes. You can learn more here on Varsity

3

Can check sensibull, they break down all premium into greeks and show exact values.