"I and my guest eat dinner together."
Translation:Mi kaj mia gasto vespermanĝas kune.
That is a common mistake in English. English distinguishes syntactically two different pronouns: me and I. 'I' is always used when it is the subject of the verb, 'me' is used elsewhere, as the object or when it stands alone.
I see a man. -> Subject of the verb -> I
A man sees me. -> Object of the verb -> me
I and a man see a woman. -> Subject (among others) of the verb -> I
A woman sees me and a man. -> Object of the verb -> me
Who has done this? -> Me. -> stand-alone
It was me. -> not the subject of the sentence.
Me! I have done it. -> 1. stand-alone, 2. subject of the verb
The same applies to the other personal pronouns that have different forms: me/I, him/he, her/she, us/we, them/they.
"Was it us or them? Have we done it or have they done it? No. It was me and you. I and you made this."
I guess the problem mostly occurs when the regarding personal pronoun stands in first place, is followed by another subject and only then the verb comes. The big gap between the first pronoun and the verb might lead speakers to assume to use the stand-alone form of the personal pronoun.
When you have more participants as subjects and aren't sure whether it is 'me' or 'I' just leave the other participants out: I/Me and my guest eat dinner. - I/Me eat dinner. - 'Me' doesn't fit here. So - I eat dinner.
I tried correcting the order in the translation since it has the same meaning but got a specific message "There is no particular grammatical reason to change the order of the constituents from the original 'Mi kaj mia gasto vespermanĝas kune', is there?". So I guess they already thought about it and I won't report it, but not sure what the point is in having "incorrect" English here.