How to get minecraft-like game to generate blocks and still run OK and not slow afterward?

I’m currently working on a Minecraft-like game called MineScape, but I have a problem of whenever blocks generate and they are done generating, the game lags like crazy. This is especially true for when I use quads to build the cube, as the game becomes almost unresponsive and otherwise extremely slow. Otherwise, cubes just slow it down to an unpalatable speed.

I know I could potentially solve the problem with quads, and that I do in fact know that I can use code to build quads, but I don’t know how to use the quads in a way that would prevent lagging the game out, and I can’t exactly find the YouTube video I want for the problem itself. I don’t want to take any more of the time required to figure it out on my own, and besides, I’ve decided that’s what I’d rather do instead of other sources, and so therefore this is why I’m asking this right now. I know it’s a bit of a dumb question, but still I could honestly use some help here.

In fact, here are some images show a little bit of that in action. Obviously, it doesn’t show that the game is lagging, but it does at least show that the game lags either with these cubes or six-fold with six quads to make up cubes. The Scene View is what’s particularly important there, so pay attention to that. But the Game View is also important in the second one, since both windows show both top and side sides of the cubes themselves, to prove that they are constructed out of quads.

Thanks for the help. Have a nice day.

For starters disable the auto-generate lighting which is probably killing you on that amount of blocks. Also you can post your code here.