I'm afraid the sleeves seem a bit too long.

我看这件衣服的袖子太长了。

We can have them altered.

我们可以改—改。

I would like my sleeves lengthened.

我想把袖子加长。

I need my suit altered.

我要改衣服。

It is too tight. I want to make loose.

这太紧了，我想把它加肥。

Can you change the buttons for me?

帮我把这些扣子换一下，可以吗?