Hello,

when I try to use more than 19 Entitys, the objects will freeze. I only can move the camera.
I build a scene with a boulder (movable) and a wall with bricks.
It works fine with 18 bricks and one boulder but not more. Who can help me?
(sry, I am a n00b)

It seem that the problem is not the number of entitys. If I use Spheres everything works fine but when I try to use boxes (for a destroyable brick construction) the problem happens again. The boxes are not extactly one on an other. (can not explain in english and do it in german: Die einzelnen Steine verschmelzen ein kleines Stück (rutschen ineinander) - if anybody can translate it - please do it)

You said the blocks "melt" together. Which version GS do you use? It could be as simple as the vertex snap is to large, it automatically aligns objects. It is possible that the bounding boxes cross which could lead to that the blocks get stuck in each other. Try to decrease the vertex snap in WED or change the bounding boxes of each block.
cheers

Sounds fine but please explain it a bit more because I am a noob and my english is not really good. I am from Germany and I use A7 Extra

I made the Bricks with MED and placed it with the Script editor

OK, then of course the vertex snap does not apply here since it is found in the A6 WED. Two things to look at then:
1/ When you initially place the blocks, make sure their position offset is large enough so that they separate a little.
2/ read up on "bounding box" in the manual. That will explain when there can be a problem with the bounding boxes.

Those would be the first two "simplest" things to check.

I think I need to use the "c_setminmax(my)"
But I have no idea how it works, there are not enought information inside the manual.

Sometimes it work, sometimes not and I can not find out a reason.
In some cases, the bricks stuck together and the physics stops.

The set minmax must be done for each model. Easiest is probably to do it when each entity is created. That is when the created entity has the me-pointer set to it. Just add the line: c_setminmax(my);. That will reset the bounding box for that particular entity. You could also set its hull to narrow.

If I put 3 rows of bricks to build a wall the 21th stuck.
c_setminmax does not help
If I put 21 Bricks on different places I do not have that problems

If I use more than 40 Bricks some slide around like ants and has no shadow.

Looks like it is improving at least. Have you done phent_settype where you can set the collision hull to ellipsoid, or have you set the entity flag my.POLYGON = on?
The Manual is your friend! Look up Hull, Collison etc.