It’s a good idea to prune birch in late summer as any later can leave this variety open to fungus, and any earlier to other pests.
This is a fairly mature tree, which is overshadowing the garden and covering the plants with sap.
This birch has been damaged by an over zealous untrained gardener
Prune off any criss-crossing branches. This tree tends to drop branches. If you have this problem then prune off any broken branches before they damage the tree. Healing can take place with a three cut method and a clean cut one quarter of an inch from the leader. Sadly, there is nothing you can do about unsightly healing wounds, except to avoid creating them, by using the three cut method in future. See my post on the three cut method, which I showed you with the maple.
For saplings prune a third of the tree in summer. Allow the tree to grow for several years before heavy pruning, as I did with the young maple. See my blog on the maple for detailed advice.