You accidentally changed the properties of Game1.cs to compile as a resource. Just change it to Compile and you will be able to compile again.
Now for loading resources, do the following: Translate Windows XNA game to Monogame.
And if you need the newest monogame(3.2): How to install Monogame 3.2 in Ubuntu 14.04?
And since you are unable to compile fonts from linux use these precompiled fonts:: https://mega.co.nz/#F!iJgSBbyZ!bxZpuAXDUsGPqlsij5mTpA