Raiding.

I hit the wall after 3 strokes loses wall a life.
But when I look at the people streaming lose the wall one life per stroke. How do I?

Depends on which tool you are using, the tier of the wall (what material it is constructed from), whether or not there are mods on the server that modify damage, and most importantly which way the wall was placed. If the wall was placed the wrong way around, it will take much more damage than if it had been placed correctly.

But I use different tools and the wall is as yet so can not