Grammatically correct?

Mi hermana es muy trabajadora?
Correct <---
Incorrect

Tengo un perro que esta muy tonto, siempre se quiere morder la cola.
Correct
Incorrect<---

Yo no estoy honesto:
Correct
Incorrect<----

No, trabajadora is a noun, not an adjective.

Sorry, pressed wrong button.

Agree, second one is incorrect

Third is correct, but "yo" is redundant.

Mi hermana es muy trabajadora?

Correct <---

Tengo un perro que está muy tonto, siempre se quiere morder la cola.
Incorrect <--- The correct form is: "Tengo un perro que está muy travieso, siempre intenta morderse la cola."

Yo no estoy honesto:
Incorrect <--- The correct form is: "No soy honesto."

To check if a sentence is grammatically correct, we need to analyze its grammar rules. Let's look at each sentence individually:

1. "Mi hermana es muy trabajadora?"

To determine if this sentence is correct, we need to consider the following grammar rules:

- Subject-verb agreement: In this case, the subject, "mi hermana" (my sister), is singular, and the verb, "es" (is), agrees with it.
- Adjective placement: The adjective "muy trabajadora" (very hardworking) is correctly placed after the noun, "hermana."

Based on these rules, the sentence "Mi hermana es muy trabajadora?" is grammatically correct.

2. "Tengo un perro que esta muy tonto, siempre se quiere morder la cola."

To evaluate the correctness of this sentence, we need to consider the following grammar rules:

- Agreeing article and noun: The article "un" agrees with the noun "perro" (dog), so this combination is correct.
- Verb tense: The verb "esta" (is) agrees with the dog, "perro." However, the verb tense "esta" suggests a temporary state, so you might consider using "es" (is) instead, as it expresses a more permanent characteristic.
- Adjective placement: The adjective "muy tonto" (very silly) is correctly placed after the noun, "perro."
- Pronoun-verb agreement: The pronoun "se" correctly refers to the subject, "perro."
- Colloquial usage: The phrase "siempre se quiere morder la cola" (always wants to bite its tail) is colloquially acceptable but may not be considered formal or standard.

Based on these rules, the sentence "Tengo un perro que esta muy tonto, siempre se quiere morder la cola" is grammatically correct, but could be improved with the suggested changes mentioned earlier.

3. "Yo no estoy honesto."

To assess the correctness of this sentence, we need to consider the following grammar rules:

- Pronoun-verb agreement: The pronoun "yo" (I) agrees with the verb "estoy" (am).
- Gender agreement: Adjectives in Spanish must agree in gender with the noun they modify. The adjective "honesto" (honest) should be in the feminine form, "honesta," if referring to a female speaker. However, if you are referring to a male speaker, then the sentence is grammatically correct.

Based on these rules, if you are a male speaker, the sentence "Yo no estoy honesto" is grammatically correct, but if you are a female speaker, it should be "Yo no estoy honesta."