You can cut it right back to make it smaller after it finishes flowering I gave mine a hard pruning about a month ago as it was getting too big, just try to maintain a nice shape as you go. Or you can dig it up completely.

My husband reduced our forsythia by half after it finished flowering. The new buds are appearing now. He got a bit carried away but it seems to be recovering.
Best
Linda

Thanks for your advice. The only thing being we've cut it right back before and it grew back twice as big!!

You do need to prune every year at least after flowering Sheilar.