https://www.theregister.co.uk/2018/07/24/apple_macos_macbook_pro_patch/

If your 2018 MacBook Pro laptop is slowing down unexpectedly, then download and install today's macOS 10.13.6 Supplemental Update, and cross your fingers.

This patch attempts to address frustrating slowdowns experienced by owners of Apple's latest top-end 13in and 15in notebooks that use eighth-generation quad and six-core Intel Core i5, i7 and i9 processors. The update frees the latest 15in MacBook Pros to run up to 70 per cent faster, and 13in Touchbar MacBook Pros up to 100 per cent faster, we're told.