Hola FerdiFernandez: The "Y" in Spanish is pronounced several different ways depending on the country or region. Many (maybe most) people pronounce it like an English "J". So that is why the Duolingo voice pronounces it like "jo". It is a correct way to pronounce "yo".
In some countries or regions, it is pronounced more like "Sho". In a few places, it is pronounced as in English, like "yo" (like Rocky would say), but that would be just a few.
"La cocina" is the kitchen. Cocina can also be used as a conjugated form of the verb cocinar, such as: "Ella cocina la cena." Usually you would use an article such as "la" or "una" or some other word(s) to provide context and/or to indicate that cocina was being used as a noun.
Are diferent ways to say the verbs. It doesn't concern just the end of the verbs or just a letter. It's the meaning of the sentence what is change.
Indicative is the normal and easy use of verbs, subjunctive change the conjugations to "that I eat, "that you read", "that he speaks", "that she drinks", "that we write", "that they have". I don't know what is the name in English to this form of verbs. But it's another.
Counjugate "cocinar" in a site and you will see that have a lot of diferences. Each one have diferent uses.
I have two questions about verb conjugation as it applies to pronouns in Duolingo. 1) Why doesn't the third person singular "el/ella" also list "it" (which I think it "lo" in Spanish)? Is "it" never used the same way as el and ella (as in, "lo come" - "it eats")? Perhaps "lo" is only used as an object pronoun and never as a subject pronoun? 2) Why are the third person plurals "ellos/ellas" listed separately from "ustedes" when the verb form seems to be the same in all cases?