Hi Ahmad,
After u run "repo init ...... -b BRANCH_NAME" , try below options while syncing
repo sync -qcj8 (with the “-c” flag flag, repo will only download the revision (branch) that is specified in the manifest, not all the branches that are on the remote server. It will thus save us quite some space, and again it will take less time to download.)
repo sync --no-tags -qcj8 (u can try the no-tags option as well)
Also as Carlo suggested, you can only sync folders of your choice instead of all.
Hope this info is helpful.