New heating boiler after 25 years

Hello dear forum,

I am a complete layman when it comes to heating technology and hope to get some guiding hints here.
We own a heating boiler from the brand Viessmann. It is the model 1601 193R.

We want to replace this. We have made a small "google" attempt to see if one can compare the systems as a layman. Unfortunately, not so easy for us.
Therefore, here are the framework conditions for the new model:
Gas
Manufacturer does not matter
Hot water storage tank (or not, if you also think that instantaneous water heating is better)
Heating circuits or operating mode controllable by smartphone
Error messages for the end user (and not only for the specialist dealer or partner) also readable via smartphone
A system that, from your point of view, is very maintenance-friendly and has good spare parts availability

We have 2 floors and a living area of 155 m2. I hope I have provided enough information to maybe be able to make a first suggestion. What we wonder is how much "kW/h" power one should pay attention to, etc.

Please forgive the layman questions once again. Thank you very much in advance for your efforts.

Regards
Lucas

Do you have internet in your heating room?
You should orient the performance on the old one, or have an HLB made, although this is not always quite easy in existing buildings.

Hello,

Internet, whether via WLAN or wired, will be available.
LG

Oh, what does HLB mean?

Heat load calculation.

Ah, great thank you very much. Does anyone already have a manufacturer or model suggestion for me?