Problem installing synapse

I recently installed Synapse on a virtual machine and it worked perfectly. Now I want to install it on a raspberry Pi 3 and I find the following problem:

Warning: W: Failed to fetch http://mirrordirector.raspbian.org/raspbian/dists/jessie-backports/main/binary-armhf/Packages 404 Not Found [IP: 93.93.128.193 80]
Warning:
Warning: W: Failed to fetch http://mirrordirector.raspbian.org/raspbian/dists/jessie-backports/contrib/binary-armhf/Packages 404 Not Found [IP: 93.93.128.193 80]
Warning:
Warning: W: Failed to fetch http://mirrordirector.raspbian.org/raspbian/dists/jessie-backports/non-free/binary-armhf/Packages 404 Not Found [IP: 93.93.128.193 80]
Warning:
Warning: E: Some index files failed to download. They have been ignored, or old ones used instead.
Warning: Failed to stop matrix-synapse.service: Unit matrix-synapse.service not loaded.
Warning: E: Unable to locate package matrix-synapse
Warning: E: Unable to locate package python-matrix-synapse-ldap3
Warning: W: Failed to fetch http://mirrordirector.raspbian.org/raspbian/dists/jessie-backports/main/binary-armhf/Packages 404 Not Found [IP: 93.93.128.193 80]
Warning:
Warning: W: Failed to fetch http://mirrordirector.raspbian.org/raspbian/dists/jessie-backports/contrib/binary-armhf/Packages 404 Not Found [IP: 93.93.128.193 80]
Warning:
Warning: W: Failed to fetch http://mirrordirector.raspbian.org/raspbian/dists/jessie-backports/non-free/binary-armhf/Packages 404 Not Found [IP: 93.93.128.193 80]
Warning:
Warning: E: Some index files failed to download. They have been ignored, or old ones used instead.
Warning: synapse has not been properly removed
Error: Installation failed

I have tried to update the system with “apt update & upgrade” and everything remains the same.
Have those repositories fallen or do I have something misconfigured?