Diagnosis of catalytic converter

Hi,
I need your help to diagnose a problem I have.
Here are the symptoms:
1. I have a "check engine" light with the code: P0420: Catalyst Efficiency Below Threshold (Bank 1).
2. Fuel efficiency has deteriorated from ~10km/liter to ~8km/liter
3. The Jimny feels weaker in the past few weeks. It's more difficult to accelerate in high speeds or uphill.
4. The engine stopped suddenly while climbing a steep slope (while in low) (happened only once)
5. Here are the readings from the O2 sensors in low and high RPM (I don't know if this is helpful):


My inexpert guess is I need to replace the catalytic converter.
Can you confirm that or maybe suggest other things to check?
Could it be that only the O2 sensors are causing this?

Thanks!

Whilst it could be a problem with one of the O2 sensors if you don't have any leaks then its more likely to be a cat problem.