Learn Spanish (Latin America): Ayudar es peligroso porque el perro está mal. - Helping is dangerous because the dog is unwell.

Porque (one word, no accent) means "because" and connects an action to its reason. If you want to ask "why?", you have to use por qué (two words, with an accent over the e).

Why does the sentence use the infinitive ayudar (to help) to mean "helping"?

In Spanish, when an action is the subject of a sentence, you always use the infinitive form like ayudar. English usually uses the "-ing" form ("helping"), but Spanish never uses its equivalent "-ando" or "-iendo" words as the subject of a sentence.

What does the adjective peligroso (dangerous) agree with here?

It describes the action of helping (ayudar). Whenever an infinitive verb is the subject of a sentence, Spanish treats it as a masculine singular noun. That is why it uses the masculine singular ending -o in peligroso.

Why do we use es for dangerous, but está for unwell?

We use es (from ser) because being dangerous is a characteristic of helping in this scenario. We use está (from estar) because being unwell is a temporary health condition. Notice that está mal means "is unwell," whereas es malo would mean "is a bad/evil dog."