Git: commit partial changes

There are multiple questions on Stack Overflow addressing the problem of staging and committing only parts from files. However, I can't make it work. - How can I commit only part of a file in git Let's say we want to implement a dummy math class in php (the language doesn't matter) with some basic methods like: `add`, `subtract`, `multiply` and `divide.` Let's start with the class definition: ``` <?php class Math { } ?> ``` Now: ``` $ git add math.php $ git commit -m "Create Math class." ``` In the next step we implement both `add` and `subtract` four methods: ``` <?php class Math { public function add($a, $b) { return $a + $b; } public function subtract($a, $b) { return $a - $b; } } ?> ``` But now we want to commit the implementation of the `add` and the `subtract` methods in separate commits. Is this possible? What I tried `$ git add -p` The following appears: I would love to split the hunk into smaller hunks, so I press `s`, and the following appears: It seems that git didn't split it into smaller hunks. Let's try now to manually edit the current hunk. So I press: `e`. My default text editor (sublime text) opens up, and here I can edit the hunk: I try to simply delete line 8,9,10,11 - because I want to stage only the `add` function. I save, close the editor, but git says: `Your edited hunk does not apply. Edit again (saying "no" discards!) [y/n]?` I'm really new to `git add -p` and interactive staging, so maybe it's something I do wrong, or simply it's not possible what I want, and really hope some more experienced git users have some instructions maybe also a solution for me. Thank you!