Doubt about forecasting

Good evening everyone,
as the title says I have a doubt about forecasting analysis.
Let's say I have a "time" variable and a "budget" variable. I would like to build two model:

  1. time series model where I forecast the budget for the next, for example, 6 months;
  2. another time series model where I forecast the next 6 months (same as above) but where I consider
    a loss of budget due to another lockdown during the months of november and december.

For 1. I would apply a standard forecasting method, but I have a doubt about number 2, what would be the right method and packages to do such thing, if possible?

I would like to do that for a thesis project but I just started to scratch the surface of time series analysis.

Thanks in advance!!