As a countryside kid, I had a lot of fun when I was young.

One way was finding a horse’s ponythailr and wouind it into a flexible knot, then fixeding it to the end of a bamboo pole, then you could tiecatch cicadas everywhere.

"Ponytail" refers to a hairstyle, not actual horse hair.

An interesting thing I still remember now is capturing cicadas.

Using "now" is redundant because you already said you "still remember" it.

Let me showtell you guys briefly.

The verb "show" is okay here, but in writing I think a verb like "tell" makes more sense because you are not literally showing us these methods. Usually "show" has a more physical connotation.

One way was finding a horse’s ponytail and wound, winding it to a flexible knot, thenand fixeding it to the end of a bamboo pole, t. Then you could tie cicadas everywhere.

In English when performing a series of actions like this they should be separated by commas and have the same verb endings, like I changed to "ing". This is called parallel structure. Your writing makes sense but this way it is more clear and flows better.

The other way was to finrequired a used washing powder plastic bag and a thin piece of wire.

This sentence does not really describe the entire method, just what you need for it so something like "required" is better than "was to find" to show this distinction.

Then wound the wire wire was wound into a ring and used it to support the opening of the plastic bag.

The next thingstep was to fix this assembly at the end of a bamboo pole, so you could use it to cover cicadas.

Alternatively you could use "thing to do" instead of "thing," but I think "step" is more succinct. Essentially "thing" on its own here is not clear enough to show you are talking about an action.

The third way was to find some wheat flour and water, then mix them together, and keep stirring until it became a sticky gluten.

First, "then" is not needed because the comma is enough to show it is a successive action. Second, "a" doesn't really work with gluten because it is an uncountable noun. The a does not have to be removed it just sounds a little off.

Then you put the gluten on the tip end of a bamboo pole, and then you could use it to stickstick the pole to cicadas.

Using "tip" and "end" is somewhat redundant because they both refer to the same place.

I think what you're trying to do is put the pole onto the cicada so it cannot escape. However, the verb "stick" in English usually means to pierce a thing with something pointed ("stick my finger with a needle"). So the meaning of this sentence would be like stabbing the cicada. The way I rewrote it makes it clear the pole is sticking TO the cicada rather than sticking it.

But remember, you should only stick the pole to their wings.

Without adding "the pole" the sentence is saying that the subject "you" should stick to the cicada wings and I don't think you mean that the person should be sticking themselves to the cicadas.

So when you saw a kid with a red belly in the summer in the countryside, that was because when he climbing trees to caughttch cicadas, the bark grazed his belly.

You probably do not need to repeat "in the countryside" again because earlier in your writing you said "as a countryside kid" so it is implied all this takes place in the countryside.