Could someone help me correct the sentences? Thanks! (¿Podría alguien ayudarme corrigiendo las siguientes oraciones? ¡Gracias!)

The main mistake you are making at the moment is that you are using subject pronouns all the time, but you should not do so. Normally, we do not say "yo ceno" or "yo estoy feliz". We normally just say "ceno" and "estoy feliz". Spanish is a "pro-drop" (pronoun drop) language, meaning that you can drop the subject pronouns unless you need to use them for emphasis.

I will give you some examples of times that you would need to use subject pronouns. You could say for example, "mi amigo está triste, pero yo estoy feliz". That would be correct, because you are emphasising the difference between you and your friend, so that is why you use a subject pronoun.

Or: "mi amigo no cena, pero yo sí ceno" would again be an example of using a subject pronoun to emphasise a difference.

Or: "a mi amigo no le gusta cocinar, pero a mi sí que me gusta" would be another example of emphasising a difference.

But usually in Spanish you should not use subject pronouns unless you need to emphasise things for some reason: usually to highlight a contrast, or to correct a mistake that somebody has made.

Here is an imaginary example of a situation that might require subject pronouns to correct a mistake in a social introduction:

Imagine that somebody says to your friend "hola, Jozing." You are surprised, because your friend is not Jozing. YOU are Jozing! So you correct the person's mistake, and you say: "no, él no es Jozing. ¡Yo soy Zozing!" because you are emphasising who Jozing really is.

Espero haberte ayudado. :)