I need to create a limited sftp user for a 3rd party company which needs to collect some data from a specific directory on a OpenSuse server.
these data are generating contentiously so they need constant connection but I need to limit their accessto only be able to transfer those data and them absolutely nothing.
please help with the approach.

Either an account with the sshd_config ChrootDirectory directive or a shell like 'rssh' (can use chroot too). BTW if you don't like to provide them access to your system there's other ways ranging from netcat, a simple Xinetd service (behind stunnel?) to streaming data to them using Syslog-NG, Rsyslog or an SSH "listener" on their system...

I'm fairly new to this too. Some of the users on our system have /usr/libexec/openssh/sftp-server as the login shell. These users can only login using sftp, not even scp. You might want to also consider chroot as suggested above. Cheers.

You can put all the users you want to restrict to SFTP into one group and then configure /etc/ssh/sshd_config to limit them to SFTP only, chrooted or not.

That will allow them SFTP and nothing else. If you need to limit them to just a particular set of directories that is easily done with ChrootDirectory, already mentioned in another post.

With ChrootDirectory there is one condition that must be met: The directory and all directories above it, on up to root, must be root-owned and not writable by any other user or group. That makes chrooting to home directories harder but still possible.