sounds like forsythia

i have one a similar size, and have reduced it by that amount over a 3 year
period, with great success. prune directly after flowering for the best
display next year.

a friend tried pruning harder than that and killed a couple of the shrubs
off in his garden.

it should then flower better than ever although mine now grows very
vigourrously, having reduced it stages i can now take off all one years
growth in one go after flowering.

chaz