"The dogs are going to the office."
Translation:Köpekler ofise gidiyor.
Tips and Notes of To Be lesson says
The suffix -lAr is optional in the 3rd person pl. However, it is only optional when referring to people. This suffix may not be used for items and animals. Only humans!
But I have seen the opposite in Duolingo
"gidiyoruz" means "we go".
Usually, the verb is third-person singular (like "gidiyor") if the subject is mentioned and is plural, as here ("köpekler").
I see in another example that there is a suffix for the object: "Hayvanat bahçesine gidiyoruz" meaning we are going to the zoo.
So why in this example there is no suffix for the "ofise"?
Both of your examples have the same suffix: -e (hayvanat bahçesinE and ofisE). The base word is ofis.
(hayvanat bahçesi has an additional linking -n- because the case marker -e comes after a possessive ending -si, but that -n- is not really part of the suffix. If you'd have a noun ending in a vowel such as büro which also means "office", you'd also get a linking consonant, in this case -y-: büroya.)
Why do is it "çocuklar gidiyorlar" but köpekler gidiyor? Are they not the same, third person plural?
When the subject is plural, the verb stays singular.
However, if the subject refers to people, then the verb may optionally get a plural marking as well.
Thus çocuklar gidiyorlar (alongside çocuklar gidiyor) but köpekler gidiyor.