Error while reduce repository size

I want to reduce the size of my repository. I work like it is described here.
At step 9 I got an error:

git push origin --force 'refs/heads/*'
Objekte aufzählen: 5671, fertig.
Zähle Objekte: 100% (5671/5671), fertig.
Delta-Kompression verwendet bis zu 4 Threads.
Komprimiere Objekte: 100% (2207/2207), fertig.
remote: fatal: pack exceeds maximum allowed size
error: Entpacken auf der Gegenseite fehlgeschlagen: index-pack abnormal exit
To git......
 ! [remote rejected] master -> master (unpacker error)
error: Fehler beim Versenden einiger Referenzen nach 'git@git.....'

(I have an german system, so the messages are not english. Is there an easy way to switch the language of my git to english to get the english messages?)

I already removed all branch protections on the server and created an new export of the project. The Gitlab server is an server of my university.

I would be thankful for any help.