Learn Spanish (Latin America): ¿Cuánta desesperación sientes por mi estupidez? - How much desperation do you feel because of my stupidity?

In Spanish, por is often used to mean "because of" or "due to" when it is followed directly by a noun (like mi estupidez) or an adjective. You would use porque (because) if you were following it with a full phrase that has a conjugated verb, like porque soy estúpido (because I am stupid).

Why is it Cuánta instead of Cuánto?

The word for "how much" changes to match the gender and number of the noun it describes. Since desesperación is a feminine singular noun, you must use the feminine singular form Cuánta. Remember that Spanish words ending in -ción are almost always feminine.

Why do we use sientes instead of the reflexive te sientes?

When you feel a specific thing (a noun, like desperation, heat, or pain), you use the standard verb sentir. You use the reflexive sentirse when you are describing how you feel using an adjective or adverb, such as te sientes desesperado (you feel desperate).

If I wanted to talk about multiple "stupidities," how would I make estupidez plural?