Use the following website to help you find and fix configuration errors:
https://yaml-online-parser.appspot.com/

org.bukkit.configuration.InvalidConfigurationException: while parsing a block mapping
 in "<string>", line 38, column 5:
        default:
        ^
expected <block end>, but found BlockMappingStart
 in "<string>", line 136, column 6:
         Admin:
         ^