Update: We are a very small team (3 people) and thus I (SM) and the PO are also developers doing some coding.

We are aware of this situation and we are actively trying to recruit some new talents. But it's hard!

Meanwhile... we need to adapt... so my question:

The PO complains about having too much outside noise (mainly stakeholders feature requests), and he can't focus on the sprint realisation.

We agree that we should try to educate people on our process implications (sprint durations and product backlog), to reduce the noise.

But as a ScrumMaster, how am I supposed to shield a PO from outside? Isn't he supposed to be in contact with the management and business?

Also, if people outside don't want to waste too much time learning agile, what is the best way to educate them?