Any co-owner may initiate an amendment, but in practice this is typically the task of the manager or the supervisory committee: collecting which points are problematic and preparing concrete, drafted proposals rather than vague calls for change.
The required majority is set in the bylaws themselves or, failing that, in the law, typically a qualified, often two thirds majority, since the bylaws record fundamental rules affecting the whole community.
The first step is an itemised review of the current text against how the building actually operates. Old bylaws often prescribe committees or procedures that have not functioned for years, while practice has developed differently.
The second step is drafting concrete text, preferably with legal expertise, because an imprecisely worded amendment can create new disputes instead of closing old ones. The proposal must be sent to owners with the invitation so they have time to study it.
A practical tip: handle amendments as a package rather than point by point, month after month, because running another meeting procedure costs time and energy.
Merbo recommends reviewing the bylaws annually together with the report, and flags to the supervisory committee when a point no longer fits how the building actually works.
A final practical aspect: the exact date of entry into force must always be recorded in the minutes, as this determines which matters fall under the old and which under the new text.