Why doesn't it work smoothly from outside the network?

[ChrisKillerKeller]

Hi togehter, I have a really smooth experience when playing in the network.
I now set up a VPN via Fritzbox and everything runs smooth like remote desktop etc.
However obviously Sunshine+Moonlight on iPad don't run smoothly via 5g and VPN anymore.
Presumably it is the internet connection. However Gamin via LAN on my Desktop i perfect, with no Latency (under 30ms always) no package loss, quick pings, etc, as I play CoD competitively and the connection is very good, I have 50 dl and 11mbit Upload. Wich should be enough for 720p 60hz.
To check, I went down to 420p and 30hz which says it only needs like 2mbit Bitrate. I have far more though but it still lags immensly and is unplayable. Where can I try to work on?? I would buy a better T-Online Connection with 40mbit upload but I doubt this will help, as in that case the lowest setting should normally already work fine with 11mbit Upload.. what do you think?