Hi,

Now isn't the right time to prune this plant. While you can safely cut off branches that are blocking the sidewalk or windows, you should wait until late fall or spring to do structural pruning. With all the leaves gone will be easier to see what you're doing.

If you cut branches all the way back to the trunk they will not come back. You can cut branches back in length by half if you want. This page and video are a good reference:

https://extension.umn.edu/trees-and-shrubs/pruning-hydrangeas

These hydrangeas are by nature fast growers. If it's a variety like "Limelight" it may grow by a third in height over the summer. These plants will bloom even if you prune them in spring.

With the old flower heads visible it looks like no one pruned this plant this year. You can easily reshape it next spring, and it will have a more rounded, manicured look.

Hope that helps!