Sales forecast and data validation

Hi all,

I was wondering if anyone can help me to improve the sales forecast that I have been doing so far.

To summarize, I have a spreadsheet with the quarter sales of several products, and I am using the FORECAST.ETS formula to predict the sales of the next two quarters. However, sometimes I believe that the results are not good, so I have to check them one by one and fix the values manually.

Also, I have too many years without studying statistics, and I am not sure what to read to help me with this.

My questions:
- Do you have a better forecast suggestion than the formula I am using (forecast.ets)?
- Is there any way to evaluate if my data points (quarter sales) are statistically reliable? for example, if sales fluctuate without any trend, I would like to know if that data is good. I want to avoid checking all the values every time that I update the sales.
- Do you have some statistics content recommendations that I can read?

Thank you in advance