How to update Git's metadata without affecting working dir?

I am working individually at the moment. I have the habit of committing related changes on a regular basis, but I push to GitLab only at the end of class session.

-------Events to reproduce the situation--------

Thursday, in school:
- `git clone https://gitlab.../my-repo`
- create a few .rst documentation files
- commit the above changes before I `git push -U origin master`

Friday, in school:
- start working on new feature, create a test file `test_A.rb`
- I commit the changes but forget to push

Sunday, **in home**:
- I `git clone https://gitlab.../my-repo`
- work on the exciting new feature that popped in my head, create `feature.rb`
- commit the changes before I `git push -U origin master`

Monday, in school:
- running `git status` shows `Your branch is ahead of 'origin/master'
by 1 commit.`

--------end problem reproduction----------------

Questions I have

1. What will happen if I follow Git's recommendation `use "git push"
to publish your local commits`?
2. How do I resolve this situation? I don't want loose any information
i.e. preserve `test_A.rb` and `feature.rb` along with their commit
messages and timestamps.
3. Why does Git assume that local-working-dir is "ahead" without
consulting the Gitlab server first?
4. How to make Git "consult" (but not mess the working-dir) GitLab
repo before starting my day's work?

Thank you.