One PO, one Backlog, one SM and two Development Teams how does it work?

Hi Marcel,

I believe the reason why Nexus is said to apply only to three or more teams is because two teams will likely find less wasteful ways to work together, e.g. they might not need an Integration team to keep track of their dependencies, seeing as there's only two teams.

Who is responsible to pull the PBI's from the prodcut backlog to the specific sprint backlog of the respective team?

The Scrum Guide has the answer as to who pulls PBI into a specific team's backlog. ;-)

Who did the refinement?

Refinement should generally be done by the team which will do the work (or as the case may be here, the team likely to do the work). I've found the benefit of refinement is in the conversations it sparks, not so much the results it produces.

It’s always important to look for reasons not to scale. Scaling brings its own problems, some of which Nexus is designed to address. The first choice should always be to descale organizational challenges so they can be dealt with using Scrum.

Where there are only two teams, there is little reason to resort to a scaling solution at all. Two Scrum Teams working on the same product ought to be able to collaborate with each other without recourse to a scaling methodology or framework.

Thank you for your help. :-)