Error: Path does not exist:'python'

[ABraun]

please have a look at this solution and add the full path to your python installation:

SNAP warning error

It is not easy to help with little information about your system, data, version… Open S2 files via File > Import > Optical > Sentinel-2 > L1C and select the xml file in the folder above. It is named like S2A_OPER_MTD_SAFL1C_PDMC[…].xml_. Select a resolution then. If step 1 is done you can open the data, make an image composite or work with individual bands. Please open Tools > Manage external tools > Sen2Cor > Edit and post a screenshot of the tab System variables