“Practicing” is the right word for this sentence. “Training” is usually used for something a person does to or for a person or thing in order to improve that person’s or thing’s abilities, and so the object of the verb “training” is a person, animal, or other object: Examples: I am training her to do the job. I am training my dog to sit on command. I am training Siri to recognize my voice. I am training myself how to read music.

Hello Kai! Both of these sentences do mean the same thing, though Sentence A sounds a bit better to me. Another option would be the verb 'to hone', which is a word we specifically use with skills: I am honing my translation skills.

Thank you Teacher Adam

The nuance is a little different actually, but they are essentially are the same thing and I would also note that [A] is the more common natural phrase. [A] refers to the idea that you have a satisfactory skill level and are keeping it at the level. [B] refers to the idea that you are trying to get your skill level higher than it already is.