Several years ago I studied English hard to improve my English.

But I stopped. Even when I did my best so much , I didn't develop my speaking skills...My skill was up only writing .

I have decided I'm going to try again.

I just try. not sure if you meant: "I just started trying again." or something like that!! anyways nice job and good luck!

Several years ago I studied English harder in order to improve my English. But I stopped. Even if I did my all of my best so much , I didn't got developing my speaking skills... My best skill was up only writing writing. I have decided I'm going to try it again. I just try.

- Harder -

You have to use "hard" since you have not compared the action of studing English with another one.

- In order to -

It is not actually wrong "to improve my English", nevertheless it is quite better if you use "in order to" inasmuch as you have a goal which is improve your English.

- All of my best -

"I did my best so much" is not toltally wrong, but it is not a really good way to express you did as much as you could.

- I didn't got developing my speaking skills -

Develop your speaking skills is a goal, so is something you want to reach or to get, therefore it is quite better express the idea like that.

- My best skill was writing -

There are just a few skills (reading, writing...) so you cannot say "my best skills". The way it is expressed in the text is not really natural.

- I have decided... -

Right now you want to try learning English again, so you have decided it, it is true that you decided it in the past, but at the present the choise continues so it is more suitable using the present perfect.

- I just try -

It is not really necessary to use it. Furthermore it makes no sense.

*Take care of the punctuation.

I wish you all the best learning English!! ❤️

Learning Englsh again !!

Several years ago I studied English hard to improve my English.

But I stopped. Even if I did my best so much , I didn't develop my speaking skills...My skill was up only writing .

I have decided I'm going to try again.

I just try.