Hrvatski jezici jezik (jezici - plural) (I'm a beginner - početnica sam (althought I would say "početnik sam" which is musculine form no matter the fact that I'm a girl; it's more common to use in this situation musculine form))

Zdravo (better Bok)! Dobar Dan dan. ja Ja se zovem Selly (or Zovem se Selly). Imam dvanaest godina. Živim u Indoneziji. Ja* mogu govorim indonezijski**, engleski, i malo hrvatski. 
Ne razumijem velika puno na hrvatskom.

* this sentence could be without pronoun "ja"; since our verbs have different forms for every person, it's not necessary to use pronouns - "govorim" is the present form of the infinitive "govoriti" and the ending -m shows that it can only be form for the first person of singular. It is the same with other example: "Ja se zovem Selly" or without pronoun "Zovem se Selly".

** names of languages we write with small letters (of course except of the beggining of the sentences).

Hrvatski jezik (jezici - plural ) ci(I'm a beginner - ja sam početnica)

Zdravo (It is better to say "bok" because it is an informal greeting) ! Dobar D dan. j Ja se zovem Selly. i Imam dvanaest godina. Živim u Indoneziji. j Ja mogu govorim I indonezijski,E engleski , i malo H hrvatski.
ne razumijem puno velika na H hrvatskom. 

I agree with Tina. You don't have to repeat so many times this "JA" because it's not nessesary.

Whatever is finished with: ski, čki, ški, it is going to be written with small letters.  

Ok, keep it up. 

If you need my classes, please, feel free to take a look at my profile and reserve a class with me. 

See you.