A method for operating a sequential combustor for a gas turbine (1, 20); the method comprising the steps of: a) providing a sequential combustor comprising: - a first combustor provided with a plurality of first burners (12, 24) fed by compressed air and configured for injecting fuel in the compressed air in a diffusion mode and in a premix mode, each first burners (12, 24) comprises at least a gas fuel nozzle fed by a gas fuel line and at least a liquid fuel nozzle fed by a liquid fuel line; - a second combustor provided with a plurality of second burners (26, 33) fed by hot gas leaving the first combustor and configured for injecting fuel in the hot gas; - a fluidly connection configured for selectively connecting the gas fuel line and liquid fuel line for allowing part of gas fuel running in the gas fuel line to enter in the liquid fuel line and to be injected by the liquid fuel nozzle b) feeding the first (12, 24) and second burners (26, 33) with a high reactive gas fuel; c) switching off at least one of the first burners (12, 24); d) operating the remaining active first burners so as to generate hybrid flames as combination of diffusion mode and premix mode; e) flowing at least part of the gas fuel running inside the gas fuel line into the liquid fuel line through the connection; a) providing a sequential combustor comprising: - a first combustor provided with a plurality of first burners (12, 24) fed by compressed air and configured for injecting fuel in the compressed air in a diffusion mode and in a premix mode, each first burners (12, 24) comprises at least a gas fuel nozzle fed by a gas fuel line and at least a liquid fuel nozzle fed by a liquid fuel line; - a second combustor provided with a plurality of second burners (26, 33) fed by hot gas leaving the first combustor and configured for injecting fuel in the hot gas; - a fluidly connection configured for selectively connecting the gas fuel line and liquid fuel line for allowing part of gas fuel running in the gas fuel line to enter in the liquid fuel line and to be injected by the liquid fuel nozzle - a first combustor provided with a plurality of first burners (12, 24) fed by compressed air and configured for injecting fuel in the compressed air in a diffusion mode and in a premix mode, each first burners (12, 24) comprises at least a gas fuel nozzle fed by a gas fuel line and at least a liquid fuel nozzle fed by a liquid fuel line; - a second combustor provided with a plurality of second burners (26, 33) fed by hot gas leaving the first combustor and configured for injecting fuel in the hot gas; - a fluidly connection configured for selectively connecting the gas fuel line and liquid fuel line for allowing part of gas fuel running in the gas fuel line to enter in the liquid fuel line and to be injected by the liquid fuel nozzle b) feeding the first (12, 24) and second burners (26, 33) with a high reactive gas fuel; c) switching off at least one of the first burners (12, 24); d) operating the remaining active first burners so as to generate hybrid flames as combination of diffusion mode and premix mode; e) flowing at least part of the gas fuel running inside the gas fuel line into the liquid fuel line through the connection;