Can I adjust bootcamp partition in mojave?

You'll need to use a utility like Winclone to change the size of the Windows partition unless you just want to remove it and start over with a new Windows installation.

 

There are tools like CampTune who say they allow resizing Bootcamp partitions.
I never tried it and do not know if it is updated for Mojave.
The newer issues of Winclone say they allow that too.
However be cautious. The only application I know to backup a Bootcamp Windows is indeed Winclone.
Backing up your MacOS or cloning it with CarbonCopyCloner or SuperDuper! is much easier.
Test your backups before changing anything to be sure your computer boots from the Mac OSX clone as it should and check if your Winclone image does the restoring of the Bootcamp as it should.
One can never be too cautious before making changes and resizing partitions inside a mac is certainly not a minor task without danger.
Ed

 

The new version of CampTune by Paragon Software works with Mojave and more importantly with the newer APFS file system. Price is still $19.95. Be sure to make a verified backup before using it or any utility. I recommend Carbon Copy Cloner for making a backup.