How can I combine many BoxCollider2D into one Collider?

Hello

I am having problems with Unity Physics because of many box colliders, How can I combine all of them into one collider?

You can compute the coordinates of the various box colliders, then use them to create single a PolygonCollider instead, by setting the pathCount for the collider, followed by SetPath with the appropriate index and coordinates as many times as needed.

What are they for? Just collisions or are some of them triggers?

Create children objects, each with their own collider. The Parent will treat their colliders as a single one.