the black lines now mixed with white and grey . if i hide parts . flying particles all around.

That seems to be the Bevel Modifier doing it’s job I think. You can turn it off and on in the viewport visualization to see if it goes away.

That is indeed, like Omar says a visualisation of the Bevel Modifier.

I usually leave it off in Edit Mode (the left of those three buttons, like a square with four vertices), because I find it a visual distraction when modeling.

That’s the whole benefit of learning here, so absolutely use it. Martin and Omar are amazing and usually answer before I even see the question. Glad you’re making your way through!