If the branches are only local, you can use -d if the branch has been merged, like
git branch -d branch-name
If the branch contains code you never plan on merging, use -D instead.
If the branch is in the upstream repo (on Bitbucket) you can remove the remote reference by
git push origin :branch-name
Also, if you’re on the Bitbucket website, you can remove branches you’ve pushed by going to the Feature branches tab under Commits on the site. There you’ll find an ellipsis icon. Click that, then choose Delete branch. Just be sure you want to drop all the changes there!
