Would really appreciate if anyone happen to know how handle missing dates in ts

The classical way for sparse date is to create those missing dates and fill them with 0s given that on those date nothing happened.

And apply to model won’t it affect the model performance?

Yes, it will. But for the better, assuming that missing data indeed signifies 0. This is often the case in retail data: stores don't usually report 0 sales for items or SKUs. If something doesn't sell, they simply omit that information.