"The food in Mohamed's restaurant is good but expensive."
Translation:اَلْأَكْل في مَطْعَم مُحَمَّد طَيِّب لٰكِنّ غالي.
They wrote it طيب لكنّ غالي. It should be طيب لكنه غالي so that the word "laakinna" has a full sentence after it: "The food is delicious but it is expensive," because that's what the word "laakinna" needs to work. If instead of "laakinna," they just said "laakin," لكن, without the small fork on the final letter, their Arabic would have sounded informal and not standard, but it wouldn't have been as bad as it is now. As it is now, it is not acceptable Arabic.
In Arabic, being possessed by something definite automatically makes the possessed thing also definite. "A restaurant of Muhammad's" is a thought that can't be expressed in Arabic except in a round-about sort of way, like by saying "أحد مطاعم محمد" ('one of Muhammad's restaurants') or something like that. Saying "restaurant of Muhammad" automatically means "the restaurant of Muhammad." Saying المطعم محمد means "The restaurant is Muhammad," since Arabic wouldn't ALLOW you to put the definite article on something that's possessed. Oh, and it's محمد, not مهمد, by the way.