Invite external business partner to collaborate in my CRM?

Invite external business partner to collaborate in my CRM?

Hi,
I am an insurance broker and have external partners which work on my contacts in certain projects. These partners are not part of my organization.
Is it possible to invite such external partners to work IN my CRM on certain contacts?

I took a look at portals but that doesnt seem to be what I am looking for.

I need them to be able to edit leads, contacts and deals which I share with them.