I've made all my game models and imported them, but, I am noticing frame lag and I think that it's most likely due to the fact all the squares in each model are separate. I've tried
ctrl + J but the problem is when I import it into unity certain faces are missing. I've also tried recalculating the normals and that doesn't work either.
Side note: I'm very new to blender, maybe a few weeks, so any other optimization advice would be great.