"I eat if you drink."
Translation:Jag äter om du dricker.
That’s because ’you’ is the subject of the clause. There are two clauses here [I eat] if [you drink] connected by the conjunction ’if’. The subject of the first clause is I and the subject of the 2nd is you, so you have to use du and not dig. It’s only dig if du is the object of the subject action, so if you would have said ’I eat you’, it would be jag äter dig.
You can't say "Jag lagar mat äter hon".
You could say something like "om jag lager mat äter hon" (if I cook, she eats.) The reason why it's in that order then is because [om jag lager mat] is then the first unit the sentence, and as we all know at this point, the second unit has to be the verb. And then the subject comes after.
[subclause] [verb] [subject]
[Om jag lager mat] [äter] [hon].
Here it's [Subject] [Verb] [Subclause]. [Jag] [äter] om [du dricker]
I got this question as the thing where you click the words to make the sentence, and I, having no clue what the correct grammar has here, ended up clicking "som du dricker". It marked it as correct and told me there was a typo in my answer. I'd never really thought about it before, but it stands to reason that the same program grades all the different sorts of questions on duolingo.