When I've had to do this I always removed branches from underneath making sure that you could not see anything had bee removed from the top, this works for the width but won't work for the height TBH I don't think you ca reduce the height.

I agree with Mg. but you do have other taller shrubs which would cover over the top. I think it is a juniper which seems to take pruning well but the more you prune the more needs to be done as there will be new growth coming up on a regular basis. I tend to snip off bits growing in a direction I do not want at any time of year. I'm not sure when a full pruning can be done (time of year) but someone will advise you.