Hi @JeekoCZ, welcome to the community! Our File and repository size limitations page has guidance about git repositories and mentions that:

We recommend repositories remain small, ideally less than 1 GB, and less than 5 GB is strongly recommended. 
Smaller repositories are faster to clone and easier to work with and maintain. 
Individual files in a repository are strictly limited to a 100 MB maximum size limit.

Are you able to check your repositories and confirm if any files exceed the 100MB per-file maximum size limit?

If it does, then you will need to either follow our Removing files from a repository’s history guide to delete the file, or use git’s Large File Storage (LFS) feature to track and store this (and any other large) files, before the repository can be pushed to GitHub.com.