diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index ad04e3aa..002c75c5 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -4,10 +4,22 @@
   You may use `composer run phpcs` and [Editorconfig-Checker](https://editorconfig-checker.github.io) to verify that.
 * Use `use` statements wherever possible instead of writing the fully qualified name.
 * Order the composer/npm dependencies alphabetically.
-* Do not use code from the [includes](./includes) directory anywhere else.
-* Please cover your code by unit tests. Code under `includes` does not require tests.
+* Do not use code from the [includes](includes) directory anywhere else.
+* Please cover your code by unit tests, our goal is to stay at 100% line coverage.
+  Code under `includes` does not require tests as it's mostly not testable and needs to be rewritten.
 * Do not use vendor prefixes like `-webkit` in styles.
-  This is done by PostCSS + Autoprefixer according to the [`.browserslistrc`](./.browserslistrc).
+  This is done by PostCSS + Autoprefixer according to the [`.browserslistrc`](.browserslistrc).
+* Translations must be abbreviated, for example `form.save`.
+  The `default.po` files contain translations that can be auto-detected using Poedit, `additional.po` contains generated messages like validations.
 
 ## Pull requests
-Please create single pull requests for every feature instead of creating one big monster of pull request containing a complete rewrite.
+* The PR should contain a short overview of the changes.
+* Before implementing bigger changes, please open an issue to discuss the feature and possible implementation options.
+* Please create single pull requests for every feature instead of creating one big monster of pull request containing a complete rewrite.
+* Squash similar commits to make the review easier.
+* For visual changes, include both before and after screenshots to easily compare and discuss changes.
+
+## Commits
+* The commit message must be meaningful. It should serve as a short overview of the changes.
+  If needed, an additional description can be provided.
+* A commit should be self-contained and result in a working Engelsystem.