When your Mac Hard drive is full of data and that is affecting its speed then you should consider a Spring clean-up. If you are using the Time Machine to create backup for your device, then you may probably delete junk files manually, however you can get some inspiration by using some simple backup deleting steps in order to create more space on the device.
In some cases, your Time Machine may send an error notification that the Backup could not completed by the Time machine”, or backup disk cannot contain the large size of the backup, or “an AA GB is required but it is not available”. The reason for these error messages could be any of the factors highlighted below however one thing remains; the junk old files can be removed from your Time machine to free more space and that also means you can create a new backup. You can follow these simple steps in deleting Time Machine Backups on your Mac device;

Step 1: Connect the Time machine to your Mac Device.
Step 2: Click on the Time Machine and bring it to the Menu bar.
Step 3: Select and tap on the “Enter Time Machine” choice
Step 4: move down to the point where the backup will be deleted.
Step 5: At the Time machine finder’s window, you must right click on the backup otherwise you can simply tap on the Cog wheel logo located on the Finder Window.
Step 6: Click on “Delete All Backups of the Time Machine backup”
Step 7” Fill in the admin password as requested.
Deleting Old Backups from your Time Machine using “tmutil” on Mac
“Tmutil” tool is one of the easiest ways of deleting backups from time machine, especially if you are tech-savvy. All you need here is how to write the ideal command prompts, unlike the earlier method that requires a presentation through the user interface- Simple follow these Tmutil Syntax steps;
Step 1: tmutil delete /TimeMachine/Drive/Path/To/OldBackup/
You may want to choose a list if directories by date in order to confirm which backup you want to delete’; thus you will create the proper path. If you don’t want to follow this method, you can simply choose the “Is” to view a list of the dates;
Step 2: Is /Volumes/TimeMachineDrive/ Backups. Backupdb/MacName/
In this case, the lists of files that can be deleted may be specific or long, for instance, if some old files that have been backed-up for some years exist, then you have to delete such files on the exact date and that may take more time than newer files. You can use the following syntax to delete old Backups using their exact dates;
Step 3: tmutil delete
/Volumes/BackupDriveName/Backups.backupdb/MacComputerName/YYYY-MM-DD-HHMMSS/
Please take note that the YYYY-MM-DD represents the year, month and date respectively.
Make sure you change the BackupDriveName to the exact drive name of the Time Machine volume, likewise you must change the McComputerName to your Mac’s name from which you want to remove the backup. The final syntax could be like this;
sudo tmutil delete /Volumes/Time Machine Backups/ Backups.
Backupdb/MacBook\ Pro/2015-05-12-172025/