Which intranet solution to choose?

Question

Work organization

Good afternoon!
Which intranet solution to choose? We need a full-fledged resource with the ability for someone inside to monitor the dynamics of events (for example, events in the regions), KPI tracking, notifying employees about the appearance of some new documents, etc.
Almost did not work with this area - Bitrix24 and Megaplan are well-known, but it is not clear whether this is. There is also https://products.office.com/ru-ru/sharepoint/colla...
Suggestions "why not write it yourself" are also accepted, but then I would like to know the approximate size of the team for this (the solution is internal and is not on the market will be sold), cost and development time.
Thanks in advance!