～ことは～ (が/けれど)

The sentence structure ～ことは～ (が/けれど) can be used when the speaker is admitting that a statement is true, but also wants to clarify it with additional remarks. I know the structure listed here looks really abstract, but the meaning is more apparent when reading example sentences.

作文を書いたことは書いたけれど、まだ間違いがたくさんあるから書き直さなくてはいけない。
While I did write my essay, it still has lots of mistakes, so I have to rewrite it.

私はテニスをすることはしますが、あまり上手じゃありません。
It's true that I play tennis, but I'm not very good at it.

このアパートは駅に近くて便利なことは便利だけれど、家賃がとても高いです。
This apartment is close to the station and convenient, but the rent is very expensive.

あの人は、いい人はいい人だけど、ちょっとがんこだね。
While he is a good person, he's also a little stubborn.

Now, it initially looks really weird to see the repetitive portions of these sentences, and I couldn't figure out what their purpose was. But after reading them a couple times, I figured out a good way of thinking about it.

Let's translate the first sentence literally. "As for writing my essay, I wrote it, but..." The second one would be, "As for me playing tennis, I do, but..." And hence we can better understand why we have that strange repetition.