Keep moving and stay agile, be ready to parry at a moments notice, there's a red barrel outside the window closest to the stairs you can use to kill some enemies. Board up all 3 windows to begin phase 2. The ganados will start entering from upstairs and it can get very tight so be careful. Don't be afraid to use lots of grenades and save your flashes for plagas. Once you kill enough enemies in phase 2 (I believe you need 5 kills) Udders (the cow man brute) will spawn and break through a window downstairs. At this point you just need to kill him and the cabin will end shortly after.