Learn German: Ich finde es schlimm, dass der Hund krank ist.

The word dass (that) is a subordinating conjunction. It introduces a dependent clause, which means it sends the conjugated verb all the way to the end of that section. In a normal main sentence, you would say der Hund ist krank, but because of dass, the verb ist is kicked to the very end.

Do I always need a comma before dass?

Yes! In German, you must always put a comma between a main clause and a subordinate clause. Since dass always starts a subordinate clause, you need a comma right before it to separate the new information from the main sentence Ich finde es schlimm.

Does schlimm just mean bad?

schlimm translates to bad, awful, or severe. It is often used to describe unfortunate situations, injuries, or illnesses. For a sad fact like a sick dog, schlimm is the perfect word to express your sympathy or concern. If you wanted to say a person behaves badly, you would usually use a different word like böse.

Why do we use finde here instead of a word like denke (think)?

In German, when you express your personal opinion or feeling about a specific situation, you usually use finden (to find). You are literally saying that you find the situation bad. While you can use denken for general thoughts, finden is the most natural choice when judging if something is good, bad, or interesting.