The default NTFS driver is RO.
There is a ntfs-3g read/write NTFS driver for FUSE in the repository.

There may also be permission issues.
I haven't used NTFS for years, but used to mount with:-
/mnt/SeagateNTFS ntfs rw,noauto,relatime,umask=22,uid=0,gid=0,nls=utf8

The default NTFS driver is RO.
There is a ntfs-3g read/write NTFS driver for FUSE in the repository.

There may also be permission issues. You may need to change uid/gid to 1000 for user pi.
I haven't used NTFS for years, but used to mount with:-
/mnt/SeagateNTFS ntfs rw,noauto,relatime,umask=22,uid=0,gid=0,nls=utf8