My name is Erik.

              Ja se zovem Erik.

Literally: I self call Erik.

How are (you)?

(because verbs are inflected in Serbian, there is no need for using pronouns because the form already tells you everything you need to know)

I am fine.

Literally: I am well.

dobro is an adverb, not an adjective.

I am 23 (twenty three) years old.

Literally:

I have 23 years. 

Ja imam 23 godina.

Good day. 

(This is a polite greeting used mostly to old people/superiors).

Ćao 

(used both as a greeting and goodbye)

Adjectives

Note: I will write adjectives in all three forms used for masculine, feminine and neuter genders. Make sure you use the masculine gender when talking about yourself, but learn all three forms because you'll need them. Here we go!

umoran, umorna, umorno

tired

I am tired: Ja sam umoran.

You are tired (to me:) Ti si umorna.

Wait for me!

Literally:

Sačekaj me!

Wait me! (direct object without prepositions)