Q.Severe Pruning For Sweet Cherry Tree
I have a Stella sweet cherry tree I haven’t pruned for the first 4 years leading branch has grown over 2 yards without branches and a cluster of branches at the top I have bean talk to severely prune it down to 8 feet from the ground is it the right thing to do? when would be the best time to do that? I live at Pittsburgh PA.

Certified GKH Gardening Expert
The heading cut of the leader should have been done in the first two years, so you have some catching up to do. This article should help:
https://www.gardeningknowhow.com/edible/fruits/cherry/cherry-tree-pruning.htm