Nothing is underlined so let's just label the parts of speech in the sentence, so that we can be of some help.
Tina or Ross - compound subject
A compound subject happens when there are two or more subjects in a sentence joined by a conjunction.
or - conjunction
A conjunction is a word that joins words, clauses, and/or phrases together.
will go out for dinner - predicate
The predicate begins with the verb phrase of the sentence and includes all the extra information that says something about the subject.
will - verb
go - verb
A verb is a word that describes and action or state of being.
There is not a compound predicate in this sentence.
