Cloudflare slows website down significantly

Hey, we have a WordPress website set up and started using Cloudflare’s free plan as CDN. This slows down our website a lot, even for remote locations far away from our server.

GTmetrix USA without CF:

GTmetrix USA with CF:

The above tests are from San Antonio USA, our server is located in Germany so CDN should usually give us quite an advantage in this case. I am aware that the first load takes longer due to caching warm up. The above tests are fairly representative.

For some reason, the integrated Cloudflare site performance tool states that loading time is only slightly above 1 second. How can this be?

Thanks in advance.