I have severalmany shoes ion my shoe shelf, but I realized I've been using only a few shoes amongpairs of them. I have many shoes on my shoe shelf, but I realized I've been using only a few pairs of them.

It's a little strange to talk about "using" shoes. It's clear what you mean, but I think I would only use the word if I was talking about a specific purpose: "I use these shoes when I'm washing my car." "These are the shoes that I use for weightlifting." I don't think I would use it as a synonym for "to wear". I suggest "many" for "several" because it sounds like a bigger number - "several shoes" could just be, like, three shoes. Not even three pairs, necessarily. And I change the second to avoid repetition and because we usually talk about pairs of shoes.

I usually use a blackn ordinary black sneaker, because it matches any kind of clothes and I really love its simple design. I usually use an ordinary black sneaker, because it matches any kind of clothes and I really love its simple design.

Adjective order. "Any kind of clothes" is a little unnatural. More likely: "it goes with anything", "it matches anything I wear", "it fits any outfit", "it suits any style".

Only in summer,And I wear sandals if it's too hot, but only in summer. And I wear sandals if it's too hot, but only in summer.

Maybe? Unclear why you chose "only" here.

I bought the black shoes two timesice, because I used the first onepair frequently and it lost strengththey fell apart. I bought the black shoes twice, because I used the first pair frequently and they fell apart.

Two times is okay but twice is more natural. "lost strength" is grammatical and it's clear what you mean but we probably wouldn't say it, we'd say they fell apart, started falling apart, came apart at the seams, started to break down, started to disintegrate, to deterioriate, or that they simply got worn out.

I will use ithem regularly as long as the shoesy are sold. I will use them regularly as long as they are sold.