Learn Turkish: Ne kadar ağır?

Nasıl means "how" when asking about the state or manner of something (like nasılsın? - how are you?). When you want to ask "how + adjective" to measure something (like how heavy, how big, how much), you use ne kadar, which literally means "what amount". So, ne kadar ağır means "what amount of heavy".

Where is the word for "is it" in this sentence?

In Turkish, you don't always need a verb like "is" for simple statements or questions about third-person subjects ("he", "she", "it"). The sentence is literally just "How much heavy?", and the "is it" is naturally understood from the context.

Since we are learning about "daha" (more), how would I ask "How much heavier is it?"?

To ask "how much heavier", you simply place daha (more) right before the adjective. The sentence becomes Ne kadar daha ağır? (literally: "What amount more heavy?").

How do I pronounce the "ğ" (soft G) in "ağır"?

The ğ (yumuşak ge) never makes a hard "g" sound. Instead, it usually lengthens the vowel before it. In ağır, it smoothly connects the two vowels, making the word sound almost like "ah-ur" with a very soft, barely noticeable glide in the middle.