why does the camera leave victoria when she talks to the receptionist?

I don't know if its LAZY writing, but it was, I'm sure, a choice made to keep up the pace toward the end.

First of all, this way, the writers didn't have to come up with some lame story, she could use.
Second, and this is more important, they could cheat with the timeline. Anybody, who has ever checked in to a hotel knows, that even if you've booked a room beforehand with passportnumber and credentials already in the system, the time it usually takes a clerk to look it up in the system, get everything ready for you to sign and tell you all, you need to know, takes a least five minutes. Here Victoria comes up WITHOUT a booking, have to tell some kind of story, convince the clerk to let her have a room, the clerk has to make a booking, make sure a room is ready at all, take down a bunch of information and still give the same information. No way that would happen as fast as it does in the movie.

Because that is the point in the movie that it is revealed that Sonne is in really bad shape (has been shot). It's a 'reveal'.

Lazy writing may be, but I rather think she bribed the night shift with an ample sum to get the suite.

SPOILERS
On a practical level, I noted there is a thank you in the credits to the Westin Hotel in Berlin. By not showing the exact nature of the story she told they also let the hotel off the hook for condoning illegal behavior, harboring (fictional) fugitives, etc. The scene works on a narrative level because she needs to get the room without showing a passport in order for the audience to think she has a chance of getting away at the end. By staying with the wounded guy we are given a hint that all is not well when he loses his hat and doesn't bother to retrieve it. And as stated above, it helps condense the time and keep the plot moving.

Because that is the point in the movie that it is revealed that Sonne is in really bad shape (has been shot). It's a 'reveal'.