– لم يأكل الطفل – يتفوق المخلص في دراسته

The sentence (the child did not eat) is analyzed as follows:
لم: a negation particle with no specific grammatical function.
يأكل: Present tense verb, negated by لم.
الطفل: Subject, with a visible damma indicating its nominative case.

The sentence (the sincere one excels in his studies) is analyzed as follows:
يتفوق: Present tense verb in the nominative case.
المخلص: Subject in the nominative case.
في: Preposition with no specific grammatical function.
دراسته: Object in the genitive case, with a visible kasra indicating its case.