how can I prevent triangles to switch on my surface when I insert a brekline?

The Terrain will always resort back to its Feature Definition's Feature Symbology setting.  You can temporarily assign it a copy of your Feature Definition (or different Feature Def) that uses a Surface Feature Symbology that has its Display Option toggled off for Triangles (e.g. Existing Boundary). Hope this helps! 

Thanks Shawn for you reply, but I'm not asking for the visibility of the triangles but rather the "direction", I'm uploading photo of the triangles before and after inserting a breakline, a spot or even the boundary all the triangles restore to the original direction they were before I switch them and then it interpolate from the top of a wall to the center of the road. 

Thanks for your help.

this is the correct way

This is the wrong one after inserting the boundary

Thanks Shawn for you reply, but I'm not asking for the visibility of the triangles but rather the "direction", I'm uploading photo of the triangles before and after inserting a breakline, a spot or even the boundary all the triangles restore to the original direction they were before I switch them and then it interpolate from the top of a wall to the center of the road. 

Thanks for your help.

this is the correct way

This is the wrong one after inserting the boundary

What version of the software?  Where did the original surface elements originate (was it imported)?   

I have version 10.10.21.04 of OpenRoads Designer CE - 2021 Release 2 Update 10 and the TIN was originally created in GeoPak and imported as a TIN 

It's probably the version of ORD that you are on. I know that ORD 2020 R1 reacted like you described, but I'm not seeing that behavior on ORD 2022 R3. The flipped faces don't revert in the latest version of ORD, and I don't know when that enhancement came into the software.