the painless way would be to format the ntfs partition as ext4 or btrfs and mount it locally via fstab (e.g. to /home/user/data); windows is gone and you can use the space. you can search on how to the two things.

the deleting and resizing of the partition is a hit/miss scenario and there’s a number of ways you can mess up your install, most of them easily recoverable but that’s not something you want to waste your productive time on. then, when you eventually upgrade (to a larger disk, new laptop, new OS, whathaveyou) you’ll copy/move your data over and be rid of this abomination.