Q.Thinning a weeping cherry
We rescued a spindly, lackluster weeping cherry in a pot a few years ago. After keeping it potted for a year or so, we put it in the garden and its growth took off. It blossoms twice a year now and this year has grown more than ever, but is losing its shape and weeping trait and getting too bushy. Having looked at advice on when to prune, it perhaps should not be now, but wondered if we could get away with thinning it out?

Here is an article that will help you.
https://www.gardeningknowhow.com/ornamental/trees/weeping-cherry/pruning-weeping-cherry.htm