Breakdown of Доктор сказал, что острое и горькое нельзя есть вечером.
Questions & Answers about Доктор сказал, что острое и горькое нельзя есть вечером.
In this sentence нельзя means must not / it is not allowed.
The structure is impersonal:
- нельзя + infinitive = it is forbidden / one must not do something.
So нельзя есть вечером is best understood as you must not eat in the evening (or one should not eat in the evening), not you are physically unable to eat. Context decides whether нельзя is prohibition or impossibility; here it is clearly prohibition or a medical recommendation.
острое and горькое are adjectives used as nouns. The full phrase would be something like:
- острая еда = spicy food
- горькая еда = bitter food
Russian often drops a generic noun like еда (food) and uses the adjective alone in the neuter singular to mean everything that is X:
- острое ≈ spicy things / spicy food
- горькое ≈ bitter things / bitter food
So острое и горькое нельзя есть = you must not eat spicy and bitter (things/foods).