Error in the static calculation, supposedly our mistake

Yes, best to tick it off and clear your head. There are far better things on a construction site in self-planning to get upset about ^^

Yep, and measure yourself more often

How long should the beam be? At 4 m, 50 cm doesn't matter, but at one meter, it probably does. The way the structural engineer acts is rubbish; that's not how you treat a client. However, a structural calculation is not a design; if this was communicated to you incorrectly, that is very frustrating. The structural calculation tells you that you need an HEB 200 and that it must be supported on the masonry by at least 30 cm. The length is to be determined with a measurement.

The fundamental question is where you got the length of the ordered steel beam from. From the structural calculation? Because the calculated dimensions in a structural analysis do not directly reflect the lengths. Example: Opening dimension: 2.01m, bearing length of the steel beam on the masonry on the left and right each 30cm Structural dimension in the calculation: 0.30/3 + 2.01 + 0.30/3 = 2.21m Length of beam to be ordered: 0.30 + 2.01 + 0.30 = 2.61m (difference 0.40m) Apart from that, it is fundamentally proper to conduct an on-site appointment for conversions to take measurements on site and determine deviations from the plan documents.

Book this to the account for the saved construction management.

That is a hint as clear as day