Errors appearing in Visual Studio after tring to attach debugger.

Peek is working inside unity as expected. But when I try to attack debbuger in visal studio 2017 around 740 errors pop up. Most of them is "That namespace" cannot be found. I didn't post this as a bug as it seems an oversight on my side. I checked if assambly references are set up properly, and that don't seem to be a problem. Could you please point me in right direction. What should I look at?