Looks like you've been cutting something like oak or sweet chestnut, although you can get the same effect cutting into potatoes!
Try washing off with plain water, then if that doesn't work; use solvol autosol to clean it up.
carbon steel and tannin ( as well as whatever is in spuds and onions too, come to think of it

) don't mix well but the tannin can be washed off easily if done before it dries.
Sharpening is just another skill, that needs to be learned and the Miki is the ideal tool to learn on.
DMT waterstones are the ultimate in sharpening kit in my opinion, however; when you're just starting, get your self some sheets of wet & dry abrasive in various grades, from say 240 to perhaps 800 or as fine as 1200 if you really want to go fine.
Glue the wet & dry to strips of MDF and keep a piece of MDF for polishing with Autosol
You can strop on mdf if you wish or use a leather belt or piece of leather glued to another bit of MDF.
hope this helps a bit anyway
R.B.