Is possible to read the memory from my phone (S6) in recovery mode?
You cannot get access to your data through stock recovery. Stock recoveries are designed to format the data and cache, and flash OTA updates. Offering shell access through recovery is a risk to user's privacy so it is naturally avoided.

That said, I had noticed in the past some low-end MTK chipset devices' stock recovery offering (could be in encryption unsupported devices only) an option to backup user data. But even that backup is stored inside phone's storage which presumes that the user can boot into Android normally and get hold of it. 

In short, you need to look elsewhere to get hold of your data. Stock recovery is no good here.