Learn Dutch: Ik ben Nederlands aan het oefenen.

This is the Dutch way to say you are doing something right now. You use a form of zijn (to be) — which is ben here — followed by aan het and the full dictionary form of the verb (the infinitive), which is oefenen. Literally, it is like saying "I am at the practicing."

Why is Nederlands placed in the middle of the sentence?

In Dutch, the aan het + verb part must go at the very end of the sentence. Because of this, the object you are practicing (Nederlands) gets pushed before it. Instead of the English word order "I am practicing Dutch," the Dutch word order is literally "I am Dutch at the practicing."

Why is the full verb oefenen used here instead of oefen for ik?

When you use the zijn aan het structure, the main action verb at the end is always the infinitive (the full dictionary form). Even though the subject is ik, you use oefenen, not oefen. The verb that actually changes to match ik is zijn, which becomes ben.

Does the word Nederlands always need a capital letter?