Осенью я часто покупаю хурму, а моя подруга — грейпфрут.

In autumn, I often buy persimmons, and my female friend buys grapefruit.

Breakdown of Осенью я часто покупаю хурму, а моя подруга — грейпфрут.

• я: I
• мой: my
• часто: often
• подруга: the friend

Questions & Answers about Осенью я часто покупаю хурму, а моя подруга — грейпфрут.

Why is осенью used here, and what case is it?

Осенью is the instrumental singular of осень (autumn/fall).

Russian often uses the instrumental form of season words as a time expression meaning in ...:

• весной = in spring
• летом = in summer
• осенью = in autumn/fall
• зимой = in winter

So Осенью я часто покупаю хурму means In autumn, I often buy persimmon(s).
You normally do not use в with these common seasonal expressions.

Why is the verb покупаю and not куплю?

Покупаю is from the imperfective verb покупать. It is used here because the sentence describes a habitual, repeated action: I often buy.

• покупаю = I buy / I am buying
• куплю = I will buy / I’ll buy once

Because часто means often, the imperfective verb is the natural choice.

What form is покупаю exactly?