There are generally two ways to complete a breath every time you do an action, such as bench press, inhaling when you push up, exhaling when you put down, and vice versa. It doesn't matter which one you feel comfortable with, usually the former.

Don't hold your breath, but breathe once. Although the feeling of holding your breath is quite severe, if you try it a few times more, you will be weak later, which will affect the training plan and effect.