improved spelling

CONTRIBUTING.md

@@ -370,11 +370,11 @@ The `iD.js` and `iD.min.js` files in this project are autogenerated - don't edit
 ## Using GitHub and git
 
 If you are new to GitHub or git you can read the [GitHub Guides](https://guides.github.com)
-"Understanding the GitHub Flow", "Git Handbook" and "Forking Projects" could be especially intresting to you.
+"Understanding the GitHub Flow", "Git Handbook" and "Forking Projects" could be especially interesting to you.
 
 ## Step by Step
 
-Addtionaly here is a step-by-step workflow example for beginners:
+Additionally here is a step-by-step workflow example for beginners:
 
 1. [Login](https://github.com/login) to your GitHub account or [create](https://services.github.com/on-demand/intro-to-github/create-github-account) a GitHub account, if you do not already have one.
 
@@ -388,24 +388,24 @@ Addtionaly here is a step-by-step workflow example for beginners:
 
 6. Edit file(s) and try your change locally (See above).
 
-7. Add Files and commit them `git add <files> ; git commit -m "Description of what you did"` .. repeat repeat as needed..
+7. Add Files and commit them `git add <files> ; git commit -m "Description of what you did"` .. repeat as needed ..
 
-8. Push Changes to your GitHub account `git push origin <working-branch-name>`. The next push also works without the branche name: `git push origin`.
+8. Push Changes to your GitHub account `git push origin <working-branch-name>`. The next push also works without the branch name: `git push origin`.
 
 9.  Go to GitHub for your fork of iD at https://github.com/<yourgithubaccount/iD. GitHub will already know about your recently pushed branch, and ask if you want to create a Pull Request for it.
 
-10. Your Pull Request will be seen by the maintainers of iD. They can merge it or ask for changes. You can update your Pull Request with Steps 7 and 8, Step 9 is only required once once per Pull Request.
+10. Your Pull Request will be seen by the maintainers of iD. They can merge it or ask for changes. You can update your Pull Request with Steps 7 and 8, Step 9 is required only once per Pull Request.
 
 ## Clean Up
 
 After your Pull Request gets merged into the main repository
-you can clean up by deleting the branch from your Github-iD-Clone and your local directory
+you can clean up by deleting the branch from your GitHub-iD-Clone and your local directory
 
-`git push --delete origin <branch_name> ; git branch -d <branch_name>`
+`git push --delete origin <working-branch-name> ; git branch -d <working-branch-name>`
 
 ## Restart with another PR after some while
 
-If you did not use your copy of iD for some while, other Pull Request gets merged and you dont have the latest version of iD. You can replace your master with whatever is in our master. If you have not done so yet: Add the main repo as an "upstream" remote:
+If you did not use your copy of iD for some while, other Pull Request gets merged and you don't have the latest version of iD. You can replace your master with whatever is in our master. If you have not done so yet: Add the main repo as an "upstream" remote:
 `git remote add upstream git@github.com:openstreetmap/iD.git`
 Then change to the master branch and get everything from upstream (the main repository)
 `git checkout master ; git fetch --all && git reset --hard upstream/master`