Hello, is there any possibility to set manually the folder where i want avast master agent download the updates?
How long it takes for the pc’s in the network start using the master agent instead of going to the avast servers?
Unfortunately, this feature isn’t available at this time. However, for what’s Now In Development, Future Product Roadmap, and to Submit Idea, please visit https://portal.productboard.com/afb/tabs/1-now-in-development
If enough people request this feature, our developer/production team may consider/prioritize adding this function in a future update.
How long it takes for the pc's in the network start using the master agent instead of going to the avast servers?
Depending upon several factors (network, computers, etc.), this process can take several minutes to several hours.
Thank you for the reply 
Absolutely! Let us know if you experience issues with the Master Agent. You may need to submit a case at https://www.avast.com/business-support-contact if we need to collect debug log files from the Master Agent device.
I am already doing it, thank you