I want to buy shoes that is kind of sneakers.

> I want to buy shoes that are a kind of sneakers.

The shoes name is tree skipper by allbirds.

> The shoes are called Tree Skippers by Allbirds.

I tried to buy the shoes before, but I could't get my size. Because It is sold out.

> I tried to buy the shoes before, but I couldn’t get my size because they were sold out.

So I will buy the shoes in the near future when It becomes on sale.

> So I will buy the shoes in the near future when they go on sale.