You can find the complete E3Ds assembly manual of the V6 hotend, which can be followed backward for disassembly. This is the stock hotend on an Original Prusa MK3S/MK2.5S/MK2S. However, as the manual works with brand new parts, it does not consider the changes that happen when being heated repeatedly to hundreds of degrees, again and again. Metal contracts and expands and thermal paste will turn crusty over time. Therefore there are some changes to the procedure when disassembling after a long time of use.
The assembly manual for the V6 is still optimal for most of this procedure, with a few exceptions. Moving backward, you are first removing the nozzle (at 280 °C) to release the heatbreak. However, this makes it harder to remove the heatbreak from the heat sink in later steps.
As the heatbreak can be quite fragile, and its threads me be damaged if you try to grip it with pliers, we recommend that you unscrew the heatsink from the heatbreak, before removing the nozzle, which locks the heatbreak in place. A Heatbreak can still bend and break so do not unscrew it at an angle. A bend will create a whole range of printing issues.
After you have unscrewed the heat sink from the heatbreak, proceed with the E3Ds assembly manual, by heating the block and unscrewing the nozzle.
Follow this procedure to resolve the issue.