I am pretty sure this is a chaste tree. You can find pruning advice here: https://www.thespruce.com/chaste-tree-growing-profile-3269206#toc-pruning

In short, cut spent flowers now if you want more whenever the go brown. In winter, cut as much off as you want, even back to the ground. If it causing problems (like hitting the window) now you can cut those parts immediately, but I would wait until winter to do a hard cut.

@nieceandtows the big bush in back is a chaste tree. You can hack on it however you like and it will grow back. I cut ours back to a stump last winter and it was 8 foot high again by mid summer.

That means you have complete freedom. You could trim off some lower branches to expose the stems and let more light to the plants around it. You could cloud prune it to artful shapes. You could tip back every branch by 30% to encourage it to be more compact. Wait for winter before doing anything major.

It's a butterflybush. Just cut it back to where you want it to be. They are extremely hard to kill.

I'd use some heavy duty loppers.