I use OBD2 Car scanner app.
Every trip of an hour it reports multiple (2 till 5) 'Misfires harmful for catalyst'.
What does this mean and is it normal to have some?

 

No it is not normal to have misfires. The car needs to be scanned and diagnosed to see which cylinder is misfiring and why. It says harmful for catalyst, this means the unburnt fuel can gather in your catalytic converter and cause it to lose efficiency more prematurely.

 

Are you seeing any other codes other than the P030X codes? Is the car running right or does it seem sluggish, getting bad mileage etc? As noted, you should limit your driving and get a proper diagnosis before any serious damage happens.

 

There are no DTC or P codes reported. I just put the sensor data in the app on the dashboard of the app. I'm not sure how reliable this is...

I drove 70 km, 1 hour combined traffic.

The app shows:

- Sensor[ECM]Misfires harmful for catalyst total: 5
- Sensors[ECM]Misfires average cyl.1: 0
- Sensors[ECM]Misfires average cyl.2: 0
- Sensors[ECM]Misfires average cyl.3: 0
- Sensors[ECM]Misfires average cyl.4: 0

 

I would get the car checked with a scanner than can communicate with all the modules and go from there. Are you using at least 91 octane gas as required by the manual?