Very nice sabre.
I bet it was made at Solingen?
It looks like, as Jordan already said, the corrosion is well on its way and so not easy to remove.
First thing to do is cleaning the blade with soft and very clean cloths and acetone or thinner.
Then use wide paper painters tape to cover the blue at the border. Looking at the spots I know this will not go very far, but start with 240 grid in little rolls as explained in the thread linked to above.
Even with the blue taped off be very careful at that point. This should get at least some of the corrosion off, but it looks like a job for 120 grid at least, maybe even 80.
So, if you are new to the cleaning and polishing game and not feeling too sure of yourself,
I would advise to only clean the blade, tape the blue off and go over the rest with something like Mothers. Remove the tape and clean again after you're done and use Renaissance Wax to protect. Whatever grid you'd use, you'll have to bring it up to 600 at least, so there will be hours of polishing. Also you cannot go back once you started. THINK BEFORE YOU START.
Oh and do not forget to clean under the langets with some cotton swabs and white spirit.
Do not use thinners or acetone here as this will destroy what is left of the red colour of the felt washer. There can be much dirt under there.
Also use smallish cloths to clean the blade and discard them after one swipe. Go gently, from under the langet to the tip in one go, discard the cloth and start again until the cloth stays clean. This has to be done for the spine and the edge too.
To clean the hilt I would use again smallish cloths and white spirit and cotton swabs for the detail. Again do not use force. You do not want to destroy what is left of the gilding.
White spirit is rather fatty and will not affect the brass oxydation. The brass will look like it was before but will be clean. Use a clean cloth to wipe of the white spirit residue and use Ren Wax to protect.
In the case of a blued sabre I would choose to leave everything intact as much as possible.
If you have any questions feel free to PM me.
Good luck!
Cheers.