Duo still not accepting "May I" which is grammatically correct English, while "Can I" is not. When 7th graders at school ask, "Can I use the bathroom?", I tell them that I'm sure they can, but if they want permission, they need to ask again....at which point they roll their eyes and say, "May I?"
The "you" is not implied. If you ask "Can I help with the farm?", you might be asking someone who has nothing to do with the farm.
- "The neighbour's house is burning. Can I help extinguish it?"
- "Why are you asking me? It's not our house. Do what you need to."
If the person receiving the help is mentioned in the Spanish sentence, you should also mention it in the English sentence.