You only need one php version and I would always advice, to totally remove all not used and not needed php-versions and modules. as well as any meta-packages. It is a common source of plenty of errors.
did you add where nextcloud have to talk to redis, like this (example):
'redis' =>
array (
'host' => '/run/redis/redis-server.sock',
'port' => 0,
'timeout' => 0,
),
did you start the redis server?
You can live see what redis does with redis-cli:
redis-cli -s /var/run/redis/redis-server.sock monitor
Here you’ll find the redis-cli manual: https://redis.io/docs/connect/cli/