Calculating COGS through FIFO method

I would suggest/recommend using a Gantt chart for that... if you're talking about your "SALES" in my terms it's my "CONSUMPTION"
here's what I did to make a FIFO of my consumptions
if you already made a database for your items. I would suggest that you could list your purchase in FIFO order from your database in another sheet. Like mine: (KOH, KCL and H2O2 are chemicals)

so, from oldest to newest date of issued date.
what I did is I insert a helper column (combination of issued date and lot number) since they're the same lot numbers.
Then I make another sheet for the consumption of those lot numbers (this sheet just contains the amount of consumption of the chemical without lot numbers).
And then another sheet for the visualization or FIFO of my chemicals: (example KOH)

as you can see on the image, I transpose my helper column of KOH to Row 1
then on row 2 is the quantity of issued chemicals
on row 3 is the remaining balance, they are already zero since I need to forecast my consumptions.
then by using a Gantt chart method.
If you could share your file here without some private datas or upload it to the cloud/drive, I can help you to make it. if this is what you're looking for.