yemek - to eat.
so why here is 'yeriz' and what is base form of word 'yeriz'?
To eat - yemek
I eat - ben yerim
You eat - sen yersin
He\she eats - o yer
We eat - biz yeriz
You eat (pl) - siz yersiniz
They eat - onlar yerler
An egg for all of us
Is "bir yumurta yeriz" OK???
Yep, that would be fine. The ending on the verb makes it clear "we" is the subject, so dropping the pronoun "biz" does not cause any confusion.
Is 'bir' the only way to say a/an ?
Yes. Turkish doesn't have the indefinite article "a/an" -- so the word for "one" stands in when it is needed.
Explain to me please how to arrange the sentence!
As in english subject verb than object.
Turkish is a Subject-Object-Verb language. Verbs are always at the end :)
When to use yerler and when to use yeriz
Yeriz with biz while yerler with onlar
What does tane stands for ?
It is a "counter" that is optional to use in Turkish. (if you can physically count the number of things you are dealing with and it isn't human, you can normally use this word...it is rarely if ever required)