Your rules may be very different to ours in Australia. Our rules (in Qld) state:
For a passenger car, passenger car derivative or ‘soft roader’ (an all-wheel drive vehicle other than MC category), the overall diameter of any alternate tyre fitted may be up to 15mm larger or 26mm smaller than that of any tyre designated by the vehicle manufacturer for that model.
Going from a 235/35 R19 to a 245/40 R19 will result in increasing your overall wheel and tyre diameter from 647mm to 679mm, that's 32mm. Way too much here, and probably too much in Finland also. The car will feel sluggish because you will be lower the final drive ratio by about 5%, and your speedo will be about 5% too low.
I went to 245/40R18 wheels and tyres, my diameter increased from 647 to just 653, only 6mm, and my speedo is less than 1% out. And it is legal.