Error: Entity 0, Brush 204: outside world(+/-4096): (1186,1644,3964)-(3584,3794,4100)
Fix - dont create brushes outside of the grid!!
Error: Entity 19, Brush 1, Side 1: plane with no normal
Fix - you've probably vertex edited the brush and its gone a bit wonky, delete and remake it
Error: Entity 19, Brush 1, Side 1: has a coplanar plane at (3165, 3310, 3664), texture {GELAENDER
Fix - invalid brush from vertex manipulation again. Look for any sides of the brush that have a vertex splitting them (e.g. a cube with one of the sides having a vertex in the middle of it, take a house shape and move the 'roof' vertex down till it forms a flat face and you'll get this error)
Error: Entity 28, Brush 4: outside world(+/-4096): (10000,-10000,3664)(10000,10000,3712)
(1.42 seconds)
Fix - Brush is invalid, which is why values are insanely high. Delete and remake.