Snekker needed - fixing supporting wall

I wanted to put cables in side the walls. After making holes, we discovered that there is no isolation. We decided to open up the walls and put the isolation. When we opened it up, we discovered that there are no supporting beams, instead there are regular planks 2cm wide. Now i need to open up almost all walls and fix it. i need estimation for work and materials as fast as possible because i am fighting with sales man to use his insurance to cover the costs