Learn Russian: Я изучаю иностранный язык.

Russian has a few different verbs for studying. Изучать is used when you are studying a specific academic subject in depth, like a language, science, or history. Учить is often used for memorizing smaller things like a vocabulary list, and учиться is usually used to talk about where you study, like at a university. Since a language is a broad subject, изучаю is the perfect choice.

Why didn't the endings for иностранный язык change if it is the direct object?

In Russian, the direct object of a sentence takes the accusative case. However, for masculine nouns, the ending only changes if the noun is alive, like a person or an animal. Because язык is a concept and not alive, its accusative form looks exactly the same as its dictionary form. The adjective иностранный just copies the noun, so it stays the same too.

The word иностранный is very long. Is there an easy way to remember it?

Yes! Many long Russian words are built by squishing smaller words together. Иностранный comes from иной, meaning other, and страна, meaning country. So it literally translates to belonging to another country. Recognizing these smaller building blocks makes vocabulary much less intimidating.

The English translation says I am studying. How would I say I study as a general habit?

You would use the exact same sentence! Russian does not have a separate continuous tense. The verb изучаю covers both I study as a general fact and I am studying at this very moment. You just use the surrounding context to figure out which one is meant.