Learn Swedish: Han köper nya plagg.

Because plagg is plural here ("garments"). When an adjective comes before a plural noun, we add an -a to the end of it. So the base form ny becomes nya.

Wait, how do we know plagg is plural? It doesn't have a plural ending like -ar or -or.

Plagg is an ett-word that ends in a consonant (ett plagg). In Swedish, these types of words don't change their form in the indefinite plural! You can tell it means "garments" (plural) and not "a garment" (singular) because of the plural adjective nya right before it. If it were singular, it would be ett nytt plagg.

The English translation says "He buys", but could this also mean "He is buying"?

Yes! Swedish doesn't have a separate "is doing" form. Han köper translates to both "He buys" (as a habit) and "He is buying" (right now).

I've noticed köper sounds like it starts with an "sh" sound. Is that right?

Yes! When the letter k comes before a soft vowel like ö (as well as e, i, y, and ä), it is pronounced with a soft "sh" or "tj" sound, rather than a hard English "k".