"My sister is helping me to make lunch."
Translation:Моя сестра помогает мне готовить обед.
When is it ok to put мне (a direct object in this case I believe) after the verb and when is it ok to put it before the verb? I used it after the verb in a pervious sentence and it was marked wrong.
Hard to say without seeing your other sentence, but it's likely that it should have been fine; word order in Russian is very flexible and often has more to do with context, emphasis, and tone, than a strict grammatical rule.
I think the other excersise you're referring to is:
я перевожу ету статью, а ты мне помогаешь.
I am also curious about differing placement of мне.
When a personal pronoun is an object (direct or indirect), it's usually put before the verb, unless it's being emphasized for some reason.
Imperfective готовить suggests that you're focusing on the process of making lunch; perfective приготовить could suggest you're more concerned with the result (maybe 'helps me get lunch made [so we can eat]). That said... when you're using an infinitive there can be overlap in the choice of aspect - sometimes either aspect can be grammatically correct, though speakers might favor one or the other given a particular context.
It's hardly a scientific study, but for what it's worth, a quick google search gave these results: помогает мне готовить - 5,590 hits помогает мне приготовить - 3670 hits
I tried checking other aspectual pairs after помогает мне and the results were pretty similar.
моя сестра помагает мне сделать обедю only 1 letter mistake and dont works anoying its not a russian lessons but ❤❤❤❤❤❤❤ "how to spell perfect in foregin language but still cant talk in it "
Why is it моя сестра помогает мне готовить обед and not моя сестра помогает меня готовить обед? Shouldn't we use genitive when the object is animate? I'm pretty sure I am animate
Many Russian verbs 'govern' (are used with) a specific case – помогать/помочь always takes the dative. Володя им помогал. Volodya was helping them. Я помогал своей сестре. I was helping my sister.
Good textbooks often give this information by including the question words in vocabulary lists; so you 'll see помогать/помочь (кому? чему?), or интересоваться (кем? чем? instrumental), for example. It's good practice to memorize this whenever you learn a new verb. :)