ExpressionBasic meaning
لَا يَزَالُContinues/remains
ثُمَّThen, in sequence
لَيَأْتِيَنَّWill surely come (emphasis)
إِنْ لَمْ يَأْكُلْهُIf he does not consume it
سَيَعُودُWill return
يَنْفُونَ عَنْهُThey remove from it
At this introductory stage, understand these expressions in the reports rather than memorizing an elaborate grammatical classification.